'\"
'\" Copyright (c) 1997 by Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: binary.n,v 1.11.2.8 2005/02/10 10:28:21 dkf Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
'\"	to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
'\"	enclosed in one large box.
'\"
'\" .BE
'\"	End of box enclosure.
'\"
'\" .CS
'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
'\"
'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four columns separated
'\"	by tabs.
'\"
'\" .SE
'\"	End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"	Start of description of a specific option.  cmdName gives the
'\"	option's name as specified in the class command, dbName gives
'\"	the option's name in the option database, and dbClass gives
'\"	the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
'\"
'\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
'\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
'\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
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.de VE
.ie n 'mc
.el \{\
.ev 2
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.ev
.\}
.nr ^v 0
..
'\"	# Special macro to handle page bottom:  finish off current
'\"	# box/sidebar if in box/sidebar mode, then invoked standard
'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
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.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
'\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
'\"	# DE - end display
.de DE
.fi
.RE
.sp
..
'\"	# SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
'\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
'\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
'\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH binary n 8.0 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
binary \- Insert and extract fields from binary strings
.SH SYNOPSIS
\fBbinary format \fIformatString \fR?\fIarg arg ...\fR?
.br
\fBbinary scan \fIstring formatString \fR?\fIvarName varName ...\fR?
.BE

.SH DESCRIPTION
.PP
This command provides facilities for manipulating binary data.  The
first form, \fBbinary format\fR, creates a binary string from normal
Tcl values.  For example, given the values 16 and 22, on a 32 bit
architecture, it might produce an 8-byte binary string consisting of
two 4-byte integers, one for each of the numbers.  The second form of
the command, \fBbinary scan\fR, does the opposite: it extracts data
from a binary string and returns it as ordinary Tcl string values.

.SH "BINARY FORMAT"
.PP
The \fBbinary format\fR command generates a binary string whose layout
is specified by the \fIformatString\fR and whose contents come from
the additional arguments.  The resulting binary value is returned.
.PP
The \fIformatString\fR consists of a sequence of zero or more field
specifiers separated by zero or more spaces.  Each field specifier is
a single type character followed by an optional numeric \fIcount\fR.
Most field specifiers consume one argument to obtain the value to be
formatted.  The type character specifies how the value is to be
formatted.  The \fIcount\fR typically indicates how many items of the
specified type are taken from the value.  If present, the \fIcount\fR
is a non-negative decimal integer or \fB*\fR, which normally indicates
that all of the items in the value are to be used.  If the number of
arguments does not match the number of fields in the format string
that consume arguments, then an error is generated.
.PP
Here is a small example to clarify the relation between the field
specifiers and the arguments:
.CS
\fBbinary format d3d {1.0 2.0 3.0 4.0} 0.1\fR
.CE
.PP
The first argument is a list of four numbers, but because of the count
of 3 for the associated field specifier, only the first three will be
used. The second argument is associated with the second field
specifier. The resulting binary string contains the four numbers 1.0,
2.0, 3.0 and 0.1.
.PP
Each type-count pair moves an imaginary cursor through the binary
data, storing bytes at the current position and advancing the cursor
to just after the last byte stored.  The cursor is initially at
position 0 at the beginning of the data.  The type may be any one of
the following characters:
.IP \fBa\fR 5
Stores a character string of length \fIcount\fR in the output string.
Every character is taken as modulo 256 (i.e. the low byte of every
character is used, and the high byte discarded) so when storing
character strings not wholly expressible using the characters \\u0000-\\u00ff,
the \fBencoding convertto\fR command should be used
first if this truncation is not desired (i.e. if the characters are
not part of the ISO 8859-1 character set.)
If \fIarg\fR has fewer than \fIcount\fR bytes, then additional zero
bytes are used to pad out the field.  If \fIarg\fR is longer than the
specified length, the extra characters will be ignored.  If
\fIcount\fR is \fB*\fR, then all of the bytes in \fIarg\fR will be
formatted.  If \fIcount\fR is omitted, then one character will be
formatted.  For example,
.RS
.CS
\fBbinary format a7a*a alpha bravo charlie\fR
.CE
will return a string equivalent to \fBalpha\\000\\000bravoc\fR.
.RE
.IP \fBA\fR 5
This form is the same as \fBa\fR except that spaces are used for
padding instead of nulls.  For example,
.RS
.CS
\fBbinary format A6A*A alpha bravo charlie\fR
.CE
will return \fBalpha bravoc\fR.
.RE
.IP \fBb\fR 5
Stores a string of \fIcount\fR binary digits in low-to-high order
within each byte in the output string.  \fIArg\fR must contain a
sequence of \fB1\fR and \fB0\fR characters.  The resulting bytes are
emitted in first to last order with the bits being formatted in
low-to-high order within each byte.  If \fIarg\fR has fewer than
\fIcount\fR digits, then zeros will be used for the remaining bits.
If \fIarg\fR has more than the specified number of digits, the extra
digits will be ignored.  If \fIcount\fR is \fB*\fR, then all of the
digits in \fIarg\fR will be formatted.  If \fIcount\fR is omitted,
then one digit will be formatted.  If the number of bits formatted
does not end at a byte boundary, the remaining bits of the last byte
will be zeros.  For example,
.RS
.CS
\fBbinary format b5b* 11100 111000011010\fR
.CE
will return a string equivalent to \fB\\x07\\x87\\x05\fR.
.RE
.IP \fBB\fR 5
This form is the same as \fBb\fR except that the bits are stored in
high-to-low order within each byte.  For example,
.RS
.CS
\fBbinary format B5B* 11100 111000011010\fR
.CE
will return a string equivalent to \fB\\xe0\\xe1\\xa0\fR.
.RE
.IP \fBh\fR 5
Stores a string of \fIcount\fR hexadecimal digits in low-to-high
within each byte in the output string.  \fIArg\fR must contain a
sequence of characters in the set ``0123456789abcdefABCDEF''.  The
resulting bytes are emitted in first to last order with the hex digits
being formatted in low-to-high order within each byte.  If \fIarg\fR
has fewer than \fIcount\fR digits, then zeros will be used for the
remaining digits.  If \fIarg\fR has more than the specified number of
digits, the extra digits will be ignored.  If \fIcount\fR is
\fB*\fR, then all of the digits in \fIarg\fR will be formatted.  If
\fIcount\fR is omitted, then one digit will be formatted.  If the
number of digits formatted does not end at a byte boundary, the
remaining bits of the last byte will be zeros.  For example,
.RS
.CS
\fBbinary format h3h* AB def\fR
.CE
will return a string equivalent to \fB\\xba\\x00\\xed\\x0f\fR.
.RE
.IP \fBH\fR 5
This form is the same as \fBh\fR except that the digits are stored in
high-to-low order within each byte.  For example,
.RS
.CS
\fBbinary format H3H* ab DEF\fR
.CE
will return a string equivalent to \fB\\xab\\x00\\xde\\xf0\fR.
.RE
.IP \fBc\fR 5
Stores one or more 8-bit integer values in the output string.  If no
\fIcount\fR is specified, then \fIarg\fR must consist of an integer
value; otherwise \fIarg\fR must consist of a list containing at least
\fIcount\fR integer elements.  The low-order 8 bits of each integer
are stored as a one-byte value at the cursor position.  If \fIcount\fR
is \fB*\fR, then all of the integers in the list are formatted.  If
the number of elements in the list is fewer than \fIcount\fR, then an
error is generated.  If the number of elements in the list is greater
than \fIcount\fR, then the extra elements are ignored.  For example,
.RS
.CS
\fBbinary format c3cc* {3 -3 128 1} 260 {2 5}\fR
.CE
will return a string equivalent to
\fB\\x03\\xfd\\x80\\x04\\x02\\x05\fR, whereas
.CS
\fBbinary format c {2 5}\fR
.CE
will generate an error.
.RE
.IP \fBs\fR 5
This form is the same as \fBc\fR except that it stores one or more
16-bit integers in little-endian byte order in the output string.  The
low-order 16-bits of each integer are stored as a two-byte value atMZNZOZPZQZRZSZTZUZVZWZXZYZZZ[Z\Z]Z^Z_Z
the cursor position with the least significant byte stored first.  For
example,
.RS
.CS
\fBbinary format s3 {3 -3 258 1}\fR
.CE
will return a string equivalent to 
\fB\\x03\\x00\\xfd\\xff\\x02\\x01\fR.
.RE
.IP \fBS\fR 5
This form is the same as \fBs\fR except that it stores one or more
16-bit integers in big-endian byte order in the output string.  For
example,
.RS
.CS
\fBbinary format S3 {3 -3 258 1}\fR
.CE
will return a string equivalent to 
\fB\\x00\\x03\\xff\\xfd\\x01\\x02\fR.
.RE
.IP \fBi\fR 5
This form is the same as \fBc\fR except that it stores one or more
32-bit integers in little-endian byte order in the output string.  The
low-order 32-bits of each integer are stored as a four-byte value at
the cursor position with the least significant byte stored first.  For
example,
.RS
.CS
\fBbinary format i3 {3 -3 65536 1}\fR
.CE
will return a string equivalent to 
\fB\\x03\\x00\\x00\\x00\\xfd\\xff\\xff\\xff\\x00\\x00\\x01\\x00\fR
.RE
.IP \fBI\fR 5
This form is the same as \fBi\fR except that it stores one or more one
or more 32-bit integers in big-endian byte order in the output string.
For example,
.RS
.CS
\fBbinary format I3 {3 -3 65536 1}\fR
.CE
will return a string equivalent to 
\fB\\x00\\x00\\x00\\x03\\xff\\xff\\xff\\xfd\\x00\\x01\\x00\\x00\fR
.RE
.IP \fBw\fR 5
.VS 8.4
This form is the same as \fBc\fR except that it stores one or more
64-bit integers in little-endian byte order in the output string.  The
low-order 64-bits of each integer are stored as an eight-byte value at
the cursor position with the least significant byte stored first.  For
example,
.RS
.CS
\fBbinary format w 7810179016327718216\fR
.CE
will return the string \fBHelloTcl\fR
.RE
.IP \fBW\fR 5
This form is the same as \fBw\fR except that it stores one or more one
or more 64-bit integers in big-endian byte order in the output string.
For example,
.RS
.CS
\fBbinary format Wc 4785469626960341345 110\fR
.CE
will return the string \fBBigEndian\fR
.VE
.RE
.IP \fBf\fR 5
This form is the same as \fBc\fR except that it stores one or more one
or more single-precision floating in the machine's native
representation in the output string.  This representation is not
portable across architectures, so it should not be used to communicate
floating point numbers across the network.  The size of a floating
point number may vary across architectures, so the number of bytes
that are generated may vary.  If the value overflows the
machine's native representation, then the value of FLT_MAX
as defined by the system will be used instead.  Because Tcl uses
double-precision floating-point numbers internally, there may be some
loss of precision in the conversion to single-precision.  For example,
on a Windows system running on an Intel Pentium processor,
.RS
.CS
\fBbinary format f2 {1.6 3.4}\fR
.CE
will return a string equivalent to 
\fB\\xcd\\xcc\\xcc\\x3f\\x9a\\x99\\x59\\x40\fR.
.RE
.IP \fBd\fR 5
This form is the same as \fBf\fR except that it stores one or more one
or more double-precision floating in the machine's native
representation in the output string.  For example, on a
Windows system running on an Intel Pentium processor,
.RS
.CS
\fBbinary format d1 {1.6}\fR
.CE
will return a string equivalent to 
\fB\\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f\fR.
.RE
.IP \fBx\fR 5
Stores \fIcount\fR null bytes in the output string.  If \fIcount\fR is
not specified, stores one null byte.  If \fIcount\fR is \fB*\fR,
generates an error.  This type does not consume an argument.  For
example,
.RS
.CS
\fBbinary format a3xa3x2a3 abc def ghi\fR
.CE
will return a string equivalent to \fBabc\\000def\\000\\000ghi\fR.
.RE
.IP \fBX\fR 5
Moves the cursor back \fIcount\fR bytes in the output string.  If
\fIcount\fR is \fB*\fR or is larger than the current cursor position,
then the cursor is positioned at location 0 so that the next byte
stored will be the first byte in the result string.  If \fIcount\fR is
omitted then the cursor is moved back one byte.  This type does not
consume an argument.  For example,
.RS
.CS
\fBbinary format a3X*a3X2a3 abc def ghi\fR
.CE
will return \fBdghi\fR.
.RE
.IP \fB@\fR 5
Moves the cursor to the absolute location in the output string
specified by \fIcount\fR.  Position 0 refers to the first byte in the
output string.  If \fIcount\fR refers to a position beyond the last
byte stored so far, then null bytes will be placed in the uninitialized
locations and the cursor will be placed at the specified location.  If
\fIcount\fR is \fB*\fR, then the cursor is moved to the current end of
the output string.  If \fIcount\fR is omitted, then an error will be
generated.  This type does not consume an argument. For example,
.RS
.CS
\fBbinary format a5@2a1@*a3@10a1 abcde f ghi j\fR
.CE
will return \fBabfdeghi\\000\\000j\fR.
.RE

.SH "BINARY SCAN"
.PP
The \fBbinary scan\fR command parses fields from a binary string,
returning the number of conversions performed.  \fIString\fR gives the
input to be parsed and \fIformatString\fR indicates how to parse it.
Each \fIvarName\fR gives the name of a variable; when a field is
scanned from \fIstring\fR the result is assigned to the corresponding
variable.
.PP
As with \fBbinary format\fR, the \fIformatString\fR consists of a
sequence of zero or more field specifiers separated by zero or more
spaces.  Each field specifier is a single type character followed by
an optional numeric \fIcount\fR.  Most field specifiers consume one
argument to obtain the variable into which the scanned values should
be placed.  The type character specifies how the binary data is to be
interpreted.  The \fIcount\fR typically indicates how many items of
the specified type are taken from the data.  If present, the
\fIcount\fR is a non-negative decimal integer or \fB*\fR, which
normally indicates that all of the remaining items in the data are to
be used.  If there are not enough bytes left after the current cursor
position to satisfy the current field specifier, then the
corresponding variable is left untouched and \fBbinary scan\fR returns
immediately with the number of variables that were set.  If there are
not enough arguments for all of the fields in the format string that
consume arguments, then an error is generated.
.PP
A similar example as with \fBbinary format\fR should explain the
relation between field specifiers and arguments in case of the binary
scan subcommand:
.CS
\fBbinary scan $bytes s3s first second\fR
.CE
.PP
This command (provided the binary string in the variable \fIbytes\fR
is long enough) assigns a list of three integers to the variable
\fIfirst\fR and assigns a single value to the variable \fIsecond\fR.
If \fIbytes\fR contains fewer than 8 bytes (i.e. four 2-byte
integers), no assignment to \fIsecond\fR will be made, and if
\fIbytes\fR contains fewer than 6 bytes (i.e. three 2-byte integers),
no assignment to \fIfirst\fR will be made.  Hence:
.CS
\fBputs [binary scan abcdefg s3s first second]\fR
\fBputs $first\fR
\fBputs $second\fR
.CE
will print (assuming neither variable is set previously):
.CS
\fB1\fR
\fB25185 25699 26213\fR
\fIcan't read "second": no such variable\fR
.CE
.PP
It is \fBimportant\fR to note that the \fBc\fR, \fBs\fR, and \fBS\fR
(and \fBi\fR and \fBI\fR on 64bit systems) will be scanned into
long data size values.  In doing this, values that have their high
bit set (0x80 for chars, 0x8000 for shorts, 0x80000000 for ints),
will be sign extended.  Thus the following will occur:
.CS
\fBset signShort [binary format s1 0x8000]\fR
\fBbinary scan $signShort s1 val; \fI# val == 0xFFFF8000\fR
.CE
If you want to produce an unsigned value, then you can mask the return 
value to the desired size.  For example, to produce an unsigned short 
value:
.CS
\fBset val [expr {$val & 0xFFFF}]; \fI# val == 0x8000\fR
.CE
.PP
Each type-count pair moves an imaginary cursor through the binary data,
reading bytes from the current position.  The cursor is initially
at position 0 at the beginning of the data.  The type may be any one of
the following characters:
.IP \fBa\fR 5
The data is a character string of length \fIcount\fR.  If \fIcount\fR
is \fB*\fR, then all of the remaining bytes in \fIstring\fR will be
scanned into the variable.  If \fIcount\fR is omitted, then one
character will be scanned.
All characters scanned will be interpreted as being in the
range \\u0000-\\u00ff so the \fBencoding convertfrom\fR command might be
needed if the string is not an ISO 8859\-1 string.
For example,
.RS
.CS
\fBbinary scan abcde\\000fghi a6a10 var1 var2\fR
.CE
will return \fB1\fR with the string equivalent to \fBabcde\\000\fR
stored in \fBvar1\fR and \fBvar2\fR left unmodified.
.RE
.IP \fBA\fR 5
This form is the same as \fBa\fR, except trailing blanks and nulls are stripped from
the scanned value before it is stored in the variable.  For example,
.RS
.CS
\fBbinary scan "abc efghi  \\000" A* var1\fR
.CE
will return \fB1\fR with \fBabc efghi\fR stored in \fBvar1\fR.
.RE
.IP \fBb\fR 5
The data is turned into a string of \fIcount\fR binary digits in
low-to-high order represented as a sequence of ``1'' and ``0''
characters.  The data bytes are scanned in first to last order with
the bits being taken in low-to-high order within each byte.  Any extra
bits in the last byte are ignored.  If \fIcount\fR is \fB*\fR, then
all of the remaining bits in \fBstring\fR will be scanned.  If
\fIcount\fR is omitted, then one bit will be scanned.  For example,
.RS
.CS
\fBbinary scan \\x07\\x87\\x05 b5b* var1 var2\fR
.CE
will return \fB2\fR with \fB11100\fR stored in \fBvar1\fR and
\fB1110000110100000\fR stored in \fBvar2\fR.
.RE
.IP \fBB\fR 5
This form is the same as \fBb\fR, except the bits are taken in
high-to-low order within each byte.  For example,
.RS
.CS
\fBbinary scan \\x70\\x87\\x05 B5B* var1 var2\fR
.CE
will return \fB2\fR with \fB01110\fR stored in \fBvar1\fR and
\fB1000011100000101\fR stored in \fBvar2\fR.
.RE
.IP \fBh\fR 5
The data is turned into a string of \fIcount\fR hexadecimal digits in
low-to-high order represented as a sequence of characters in the set
``0123456789abcdef''.  The data bytes are scanned in first to last
order with the hex digits being taken in low-to-high order within each
byte.  Any extra bits in the last byte are ignored.  If \fIcount\fR
is \fB*\fR, then all of the remaining hex digits in \fBstring\fR will be
scanned.  If \fIcount\fR is omitted, then one hex digit will be
scanned.  For example,
.RS
.CS
\fBbinary scan \\x07\\x86\\x05 h3h* var1 var2\fR
.CE
will return \fB2\fR with \fB706\fR stored in \fBvar1\fR and
\fB50\fR stored in \fBvar2\fR.
.RE
.IP \fBH\fR 5
This form is the same as \fBh\fR, except the digits are taken in
high-to-low order within each byte.  For example,
.RS
.CS
\fBbinary scan \\x07\\x86\\x05 H3H* var1 var2\fR
.CE
will return \fB2\fR with \fB078\fR stored in \fBvar1\fR and
\fB05\fR stored in \fBvar2\fR.
.RE
.IP \fBc\fR 5
The data is turned into \fIcount\fR 8-bit signed integers and stored
in the corresponding variable as a list. If \fIcount\fR is \fB*\fR,
then all of the remaining bytes in \fBstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 8-bit integer will be scanned.  For
example,
.RS
.CS
\fBbinary scan \\x07\\x86\\x05 c2c* var1 var2\fR
.CE
will return \fB2\fR with \fB7 -122\fR stored in \fBvar1\fR and \fB5\fR
stored in \fBvar2\fR.  Note that the integers returned are signed, but
they can be converted to unsigned 8-bit quantities using an expression
like:
.CS
\fBexpr { $num & 0xff }\fR
.CE
.RE
.IP \fBs\fR 5
The data is interpreted as \fIcount\fR 16-bit signed integers
represented in little-endian byte order.  The integers are stored in
the corresponding variable as a list.  If \fIcount\fR is \fB*\fR, then
all of the remaining bytes in \fBstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 16-bit integer will be scanned.  For
example,
.RS
.CS
\fBbinary scan \\x05\\x00\\x07\\x00\\xf0\\xff s2s* var1 var2\fR
.CE
will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR
stored in \fBvar2\fR.  Note that the integers returned are signed, but
they can be converted to unsigned 16-bit quantities using an expression
like:
.CS
\fBexpr { $num & 0xffff }\fR
.CE
.RE
.IP \fBS\fR 5
This form is the same as \fBs\fR except that the data is interpreted
as \fIcount\fR 16-bit signed integers represented in big-endian byte
order.  For example,
.RS
.CS
\fBbinary scan \\x00\\x05\\x00\\x07\\xff\\xf0 S2S* var1 var2\fR
.CE
will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR
stored in \fBvar2\fR. 
.RE
.IP \fBi\fR 5
The data is interpreted as \fIcount\fR 32-bit signed integers
represented in little-endian byte order.  The integers are stored in
the corresponding variable as a list.  If \fIcount\fR is \fB*\fR, then
all of the remaining bytes in \fBstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 32-bit integer will be scanned.  For
example,
.RS
.CS
\fBbinary scan \\x05\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\xf0\\xff\\xff\\xff i2i* var1 var2\fR
.CE
will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR
stored in \fBvar2\fR.  Note that the integers returned are signed, but
they can be converted to unsigned 32-bit quantities using an expression
like:
.CS
\fBexpr { $num & 0xffffffff }\fR
.CE
.RE
.IP \fBI\fR 5
This form is the same as \fBI\fR except that the data is interpreted
as \fIcount\fR 32-bit signed integers represented in big-endian byte
order.  For example,
.RS
.CS
\fBbinary scan \\x00\\x00\\x00\\x05\\x00\\x00\\x00\\x07\\xff\\xff\\xff\\xf0 I2I* var1 var2\fR
.CE
will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR
stored in \fBvar2\fR.
.RE
.IP \fBw\fR 5
.VS 8.4
The data is interpreted as \fIcount\fR 64-bit signed integers
represented in little-endian byte order.  The integers are stored in
the corresponding variable as a list.  If \fIcount\fR is \fB*\fR, then
all of the remaining bytes in \fBstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 64-bit integer will be scanned.  For
example,
.RS
.CS
\fBbinary scan \\x05\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\xf0\\xff\\xff\\xff wi* var1 var2\fR
.CE
will return \fB2\fR with \fB30064771077\fR stored in \fBvar1\fR and
\fB-16\fR stored in \fBvar2\fR.  Note that the integers returned are
signed and cannot be represented by Tcl as unsigned values.
.RE
.IP \fBW\fR 5
This form is the same as \fBw\fR except that the data is interpreted
as \fIcount\fR 64-bit signed integers represented in big-endian byte
order.  For example,
.RS
.CS
\fBbinary scan \\x00\\x00\\x00\\x05\\x00\\x00\\x00\\x07\\xff\\xff\\xff\\xf0 WI* var1 var2\fR
.CE
will return \fB2\fR with \fB21474836487\fR stored in \fBvar1\fR and \fB-16\fR
stored in \fBvar2\fR.
.VE
.RE
.IP \fBf\fR 5
The data is interpreted as \fIcount\fR single-precision floating point
numbers in the machine's native representation.  The floating point
numbers are stored in the corresponding variable as a list.  If
\fIcount\fR is \fB*\fR, then all of the remaining bytes in
\fBstring\fR will be scanned.  If \fIcount\fR is omitted, then one
single-precision floating point number will be scanned.  The size of a
floating point number may vary across architectures, so the number of
bytes that are scanned may vary.  If the data does not represent a
valid floating point number, the resulting value is undefined and
compiler dependent.  For example, on a Windows system running on an
Intel Pentium processor,
.RS
.CS
\fBbinary scan \\x3f\\xcc\\xcc\\xcd f var1\fR
.CE
will return \fB1\fR with \fB1.6000000238418579\fR stored in
\fBvar1\fR.
.RE
.IP \fBd\fR 5
This form is the same as \fBf\fR except that the data is interpreted
as \fIcount\fR double-precision floating point numbers in the
machine's native representation. For example, on a Windows system
running on an Intel Pentium processor,
.RS
.CS
\fBbinary scan \\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f d var1\fR
.CE
will return \fB1\fR with \fB1.6000000000000001\fR
stored in \fBvar1\fR.
.RE
.IP \fBx\fR 5
Moves the cursor forward \fIcount\fR bytes in \fIstring\fR.  If
\fIcount\fR is \fB*\fR or is larger than the number of bytes after the
current cursor cursor position, then the cursor is positioned after
the last byte in \fIstring\fR.  If \fIcount\fR is omitted, then the
cursor is moved forward one byte.  Note that this type does not
consume an argument.  For example,
.RS
.CS
\fBbinary scan \\x01\\x02\\x03\\x04 x2H* var1\fR
.CE
will return \fB1\fR with \fB0304\fR stored in \fBvar1\fR.
.RE
.IP \fBX\fR 5
Moves the cursor back \fIcount\fR bytes in \fIstring\fR.  If
\fIcount\fR is \fB*\fR or is larger than the current cursor position,
then the cursor is positioned at location 0 so that the next byte
scanned will be the first byte in \fIstring\fR.  If \fIcount\fR
is omitted then the cursor is moved back one byte.  Note that this
type does not consume an argument.  For example,
.RS
.CS
\fBbinary scan \\x01\\x02\\x03\\x04 c2XH* var1 var2\fR
.CE
will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR
stored in \fBvar2\fR.
.RE
.IP \fB@\fR 5
Moves the cursor to the absolute location in the data string specified
by \fIcount\fR.  Note that position 0 refers to the first byte in
\fIstring\fR.  If \fIcount\fR refers to a position beyond the end of
\fIstring\fR, then the cursor is positioned after the last byte.  If
\fIcount\fR is omitted, then an error will be generated.  For example,
.RS
.CS
\fBbinary scan \\x01\\x02\\x03\\x04 c2@1H* var1 var2\fR
.CE
will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR
stored in \fBvar2\fR.
.RE
.SH "PLATFORM ISSUES"
Sometimes it is desirable to format or scan integer values in the
native byte order for the machine.  Refer to the \fBbyteOrder\fR
element of the \fBtcl_platform\fR array to decide which type character
to use when formatting or scanning integers.
.SH EXAMPLES
This is a procedure to write a Tcl string to a binary-encoded channel as
UTF-8 data preceded by a length word:
.CS
proc writeString {channel string} {
    set data [encoding convertto utf-8 $string]
    puts -nonewline [\fBbinary format\fR Ia* \e
            [string length $data] $data]
}
.CE
.PP
This procedure reads a string from a channel that was written by the
previously presented \fBwriteString\fR procedure:
.CS
proc readString {channel} {
    if {![\fBbinary scan\fR [read $channel 4] I length]} {
        error "missing length"
    }
    set data [read $channel $length]
    return [encoding convertfrom utf-8 $data]
}
.CE

.SH "SEE ALSO"
format(n), scan(n), tclvars(n)

.SH KEYWORDS
binary, format, scan
'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: incr.n,v 1.3.18.1 2004/10/27 12:52:40 dkf Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
'\"	to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
'\"	enclosed in one large box.
'\"
'\" .BE
'\"	End of box enclosure.
'\"
'\" .CS
'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
'\"
'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four columns separated
'\"	by tabs.
'\"
'\" .SE
'\"	End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"	Start of description of a specific option.  cmdName gives the
'\"	option's name as specified in the class command, dbName gives
'\"	the option's name in the option database, and dbClass gives
'\"	the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
'\"
'\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
'\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
'\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
'\"	# VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.ev 2
.nf
.ti 0
.mk ^t
\h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
.sp -1
.fi
.ev
.\}
.nr ^v 0
..
'\"	# Special macro to handle page bottom:  finish off current
'\"	# box/sidebar if in box/sidebar mode, then invoked standard
'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
.bp
'fi
.ev
.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
'\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
'\"	# DE - end display
.de DE
.fi
.RE
.sp
..
'\"	# SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
'\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
'\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
'\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH incr n "" Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
incr \- Increment the value of a variable
.SH SYNOPSIS
\fBincr \fIvarName \fR?\fIincrement\fR?
.BE

.SH DESCRIPTION
.PP
Increments the value stored in the variable whose name is \fIvarName\fR.
The value of the variable must be an integer.
If \fIincrement\fR is supplied then its value (which must be an
integer) is added to the value of variable \fIvarName\fR;  otherwise
1 is added to \fIvarName\fR.
The new value is stored as a decimal string in variable \fIvarName\fR
and also returned as result.
.SH EXAMPLES
Add one to the contents of the variable \fIx\fR:
.CS
\fBincr\fR x
.CE
.PP
Add 42 to the contents of the variable \fIx\fR:
.CS
\fBincr\fR x 42
.CE
.PP
Add the contents of the variable \fIy\fR to the contents of the
variable \fIx\fR:
.CS
\fBincr\fR x $y
.CE
.PP
Add nothing at all to the variable \fIx\fR (often useful for checking
whether an argument to a procedure is actually numeric and generating
an error if it is not):
.CS
\fBincr\fR x 0
.CE

.SH "SEE ALSO"
expr(n)

.SH KEYWORDS
add, increment, variable, value
'\"
'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: safe.n,v 1.4.2.1 2004/10/27 14:23:58 dkf Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
'\"	to .AP later.  If args are omitted, default tab stops are used.
'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
'\"	enclosed in one large box.
'\"
'\" .BE
'\"	End of box enclosure.
'\"
'\" .CS
'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
'\"
'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four columns separated
'\"	by tabs.
'\"
'\" .SE
'\"	End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\"	Start of description of a specific option.  cmdName gives the
'\"	option's name as specified in the class command, dbName gives
'\"	the option's name in the option database, and dbClass gives
'\"	the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
'\"
'\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
'\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1	\\fI\\$2\\fP	(\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
'\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
'\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
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.RE
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.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
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.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR manual entry for details on the standard options.
..
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.de OP
.LP
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Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
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.de UL
\\$1\l'|0\(ul'\\$2
..
.TH "Safe Tcl" n 8.0 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Safe\ Base \- A mechanism for creating and manipulating safe interpreters.
.SH SYNOPSIS
\fB::safe::interpCreate\fR ?\fIslave\fR? ?\fIoptions...\fR?
.sp
\fB::safe::interpInit\fR \fIslave\fR ?\fIoptions...\fR?
.sp
\fB::safe::interpConfigure\fR \fIslave\fR ?\fIoptions...\fR?
.sp
\fB::safe::interpDelete\fR \fIslave\fR
.sp
\fB::safe::interpAddToAccessPath\fR \fIslave\fR \fIdirectory\fR
.sp
\fB::safe::interpFindInAccessPath\fR \fIslave\fR \fIdirectory\fR
.sp
\fB::safe::setLogCmd\fR ?\fIcmd arg...\fR?
.SH OPTIONS
.PP
?\fB\-accessPath\fR \fIpathList\fR?
?\fB\-statics\fR \fIboolean\fR? ?\fB\-noStatics\fR?
?\fB\-nested\fR \fIboolean\fR? ?\fB\-nestedLoadOk\fR?
?\fB\-deleteHook\fR \fIscript\fR?
.BE

.SH DESCRIPTION
Safe Tcl is a mechanism for executing untrusted Tcl scripts
safely and for providing mediated access by such scripts to
potentially dangerous functionality.
.PP
The Safe Base ensures that untrusted Tcl scripts cannot harm the
hosting application.
The Safe Base prevents integrity and privacy attacks. Untrusted Tcl
scripts are prevented from corrupting the state of the hosting
application or computer. Untrusted scripts are also prevented from
disclosing information stored on the hosting computer or in the
hosting application to any party.
.PP
The Safe Base allows a master interpreter to create safe, restricted
interpreters that contain a set of predefined aliases for the \fBsource\fR,
\fBload\fR, \fBfile\fR, \fBencoding\fR, and \fBexit\fR commands and
are able to use the auto-loading and package mechanisms.
.PP
No knowledge of the file system structure is leaked to the
safe interpreter, because it has access only to a virtualized path
containing tokens. When the safe interpreter requests to source a file, it
uses the token in the virtual path as part of the file name to source; the
master interpreter transparently 
translates the token into a real directory name and executes the 
requested operation (see the section \fBSECURITY\fR below for details).
Different levels of security can be selected by using the optional flags
of the commands described below.
.PP
All commands provided in the master interpreter by the Safe Base reside in
the \fBsafe\fR namespace:

.SH COMMANDS
The following commands are provided in the master interpreter:
.TP
\fB::safe::interpCreate\fR ?\fIslave\fR? ?\fIoptions...\fR?
Creates a safe interpreter, installs the aliases described in the section
\fBALIASES\fR and initializes the auto-loading and package mechanism as
specified by the supplied \fBoptions\fR.
See the \fBOPTIONS\fR section below for a description of the
optional arguments.
If the \fIslave\fR argument is omitted, a name will be generated.
\fB::safe::interpCreate\fR always returns the interpreter name.
.TP
\fB::safe::interpInit\fR \fIslave\fR ?\fIoptions...\fR?
This command is similar to \fBinterpCreate\fR except it that does not
create the safe interpreter. \fIslave\fR must have been created by some
other means, like \fBinterp create \-safe\fR.
.TP
\fB::safe::interpConfigure\fR \fIslave\fR ?\fIoptions...\fR?
If no \fIoptions\fR are given, returns the settings for all options for the
named safe interpreter as a list of options and their current values
for that \fIslave\fR. 
If a single additional argument is provided,
it will return a list of 2 elements \fIname\fR and \fIvalue\fR where
\fIname\fR is the full name of that option and \fIvalue\fR the current value
for that option and the \fIslave\fR.
If more than two additional arguments are provided, it will reconfigure the
safe interpreter and change each and only the provided options.
See the section on \fBOPTIONS\fR below for options description.
Example of use:
.RS
.CS
# Create a new interp with the same configuration as "$i0" :
set i1 [eval safe::interpCreate [safe::interpConfigure $i0]]
# Get the current deleteHook
set dh [safe::interpConfigure $i0  \-del]
# Change (only) the statics loading ok attribute of an interp
# and its deleteHook (leaving the rest unchanged) :
safe::interpConfigure $i0  \-delete {foo bar} \-statics 0 ;
.CE
.RE
.TP
\fB::safe::interpDelete\fR \fIslave\fR
Deletes the safe interpreter and cleans up the corresponding  
master interpreter data structures.
If a \fIdeleteHook\fR script was specified for this interpreter it is
evaluated before the interpreter is deleted, with the name of the
interpreter as an additional argument.
.TP
\fB::safe::interpFindInAccessPath\fR \fIslave\fR \fIdirectory\fR
This command finds and returns the token for the real directory
\fIdirectory\fR in the safe interpreter's current virtual access path.
It generates an error if the directory is not found.
Example of use:
.RS
.CS
$slave eval [list set tk_library [::safe::interpFindInAccessPath $name $tk_library]]
.CE
.RE
.TP
\fB::safe::interpAddToAccessPath\fR \fIslave\fR \fIdirectory\fR
This command adds \fIdirectory\fR to the virtual path maintained for the
safe interpreter in the master, and returns the token that can be used in
the safe interpreter to obtain access to files in that directory.
If the directory is already in the virtual path, it only returns the token
without adding the directory to the virtual path again.
Example of use:
.RS
.CS
$slave eval [list set tk_library [::safe::interpAddToAccessPath $name $tk_library]]
.CE
.RE
.TP
\fB::safe::setLogCmd\fR ?\fIcmd arg...\fR?
This command installs a script that will be called when interesting
life cycle events occur for a safe interpreter.
When called with no arguments, it returns the currently installed script.
When called with one argument, an empty string, the currently installed
script is removed and logging is turned off.
The script will be invoked with one additional argument, a string
describing the event of interest.
The main purpose is to help in debugging safe interpreters.
Using this facility you can get complete error messages while the safe
interpreter gets only generic error messages.
This prevents a safe interpreter from seeing messages about failures
and other events that might contain sensitive information such as real
directory names.
.RS
Example of use:
.CS
::safe::setLogCmd puts stderr
.CE
Below is the output of a sample session in which a safe interpreter
attempted to source a file not found in its virtual access path.
Note that the safe interpreter only received an error message saying that
the file was not found:
.CS
NOTICE for slave interp10 : Created
NOTICE for slave interp10 : Setting accessPath=(/foo/bar) staticsok=1 nestedok=0 deletehook=()
NOTICE for slave interp10 : auto_path in interp10 has been set to {$p(:0:)}
ERROR for slave interp10 : /foo/bar/init.tcl: no such file or directory
.CE
.RE

.SH OPTIONS
The following options are common to 
\fB::safe::interpCreate\fR, \fB::safe::interpInit\fR, 
and \fB::safe::interpConfigure\fR.
Any option name can be abbreviated to its minimal 
non-ambiguous name.
Option names are not case sensitive.
.TP 
\fB\-accessPath\fR \fIdirectoryList\fR
This option sets the tZuZvZwZxZyZzZ{Z|Zlist of directories from which the safe interpreter
can \fBsource\fR and \fBload\fR files.
If this option is not specified, or if it is given as the
empty list, the safe interpreter will use the same directories as its
master for auto-loading.
See the section \fBSECURITY\fR below for more detail about virtual paths, 
tokens and access control.
.TP
\fB\-statics\fR \fIboolean\fR
This option specifies if the safe interpreter will be allowed
to load statically linked packages (like \fBload {} Tk\fR).
The default value is \fBtrue\fR : 
safe interpreters are allowed to load statically linked packages.
.TP
\fB\-noStatics\fR
This option is a convenience shortcut for \fB-statics false\fR and
thus specifies that the safe interpreter will not be allowed
to load statically linked packages.
.TP
\fB\-nested\fR \fIboolean\fR
This option specifies if the safe interpreter will be allowed
to load packages into its own sub-interpreters.
The default value is \fBfalse\fR : 
safe interpreters are not allowed to load packages into
their own sub-interpreters.
.TP
\fB\-nestedLoadOk\fR
This option is a convenience shortcut for \fB-nested true\fR and
thus specifies the safe interpreter will be allowed
to load packages into its own sub-interpreters.
.TP 
\fB\-deleteHook\fR \fIscript\fR
When this option is given a non-empty \fIscript\fR, it will be
evaluated in the master with the name of
the safe interpreter as an additional argument
just before actually deleting the safe interpreter.
Giving an empty value removes any currently installed deletion hook
script for that safe interpreter.
The default value (\fB{}\fR) is not to have any deletion call back.
.SH ALIASES
The following aliases are provided in a safe interpreter:
.TP
\fBsource\fR \fIfileName\fR
The requested file, a Tcl source file, is sourced into the safe interpreter
if it is found.
The \fBsource\fR alias can only source files from directories in
the virtual path for the safe interpreter. The \fBsource\fR alias requires
the safe interpreter to
use one of the token names in its virtual path to denote the directory in
which the file to be sourced can be found.
See the section on \fBSECURITY\fR for more discussion of restrictions on
valid filenames.
.TP
\fBload\fR \fIfileName\fR
The requested file, a shared object file, is dynamically loaded into the
safe interpreter if it is found.
The filename must contain a token name mentioned in the virtual path for
the safe interpreter for it to be found successfully.
Additionally, the shared object file must contain a safe entry point; see
the manual page for the \fBload\fR command for more details.
.TP
\fBfile\fR ?\fIsubCmd args...\fR?
The \fBfile\fR alias provides access to a safe subset of the subcommands of
the \fBfile\fR command; it allows only \fBdirname\fR, \fBjoin\fR,
\fBextension\fR, \fBroot\fR, \fBtail\fR, \fBpathname\fR and \fBsplit\fR
subcommands. For more details on what these subcommands do see the manual
page for the \fBfile\fR command.
.TP
\fBencoding\fR ?\fIsubCmd args...\fR?
The \fBencoding\fR alias provides access to a safe subset of the
subcommands of the \fBencoding\fR command;  it disallows setting of
the system encoding, but allows all other subcommands including
\fBsystem\fR to check the current encoding.
.TP
\fBexit\fR
The calling interpreter is deleted and its computation is stopped, but the
Tcl process in which this interpreter exists is not terminated.

.SH SECURITY
The Safe Base does not attempt to completely prevent annoyance and
denial of service attacks. These forms of attack prevent the
application or user from temporarily using the computer to perform
useful work, for example by consuming all available CPU time or
all available screen real estate.
These attacks, while aggravating, are deemed to be of lesser importance
in general than integrity and privacy attacks that the Safe Base
is to prevent.
.PP
The commands available in a safe interpreter, in addition to
the safe set as defined in \fBinterp\fR manual page, are mediated aliases
for \fBsource\fR, \fBload\fR, \fBexit\fR, and safe subsets of
\fBfile\fR and \fBencoding\fR. The safe interpreter can also auto-load
code and it can request that packages be loaded.
.PP
Because some of these commands access the local file system, there is a
potential for information leakage about its directory structure.
To prevent this, commands that take file names as arguments in a safe
interpreter use tokens instead of the real directory names.
These tokens are translated to the real directory name while a request to,
e.g., source a file is mediated by the master interpreter.
This virtual path system is maintained in the master interpreter for each safe
interpreter created by \fB::safe::interpCreate\fR or initialized by
\fB::safe::interpInit\fR and
the path maps tokens accessible in the safe interpreter into real path
names on the local file system thus preventing safe interpreters 
from gaining knowledge about the
structure of the file system of the host on which the interpreter is
executing.
The only valid file names arguments
for the \fBsource\fR and \fBload\fR aliases provided to the slave
are path in the form of 
\fB[file join \fR\fItoken filename\fR\fB]\fR (i.e. when using the
native file path formats: \fItoken\fR\fB/\fR\fIfilename\fR
on Unix, \fItoken\fR\fB\\\fIfilename\fR on Windows, 
and \fItoken\fR\fB:\fR\fIfilename\fR on the Mac),
where \fItoken\fR is representing one of the directories 
of the \fIaccessPath\fR list and \fIfilename\fR is
one file in that directory (no sub directories access are allowed).
.PP
When a token is used in a safe interpreter in a request to source or
load a file, the token is checked and
translated to a real path name and the file to be
sourced or loaded is located on the file system.
The safe interpreter never gains knowledge of the actual path name under
which the file is stored on the file system.
.PP
To further prevent potential information leakage from sensitive files that
are accidentally included in the set of files that can be sourced by a safe
interpreter, the \fBsource\fR alias restricts access to files
meeting the following constraints: the file name must
fourteen characters or shorter, must not contain more than one dot ("\fB.\fR"),
must end up with the extension \fB.tcl\fR or be called \fBtclIndex\fR.
.PP
Each element of the initial access path
list will be assigned a token that will be set in
the slave \fBauto_path\fR and the first element of that list will be set as
the \fBtcl_library\fR for that slave.
.PP
If the access path argument is not given or is the empty list, 
the default behavior is to let the slave access the same packages
as the master has access to (Or to be more precise: 
only packages written in Tcl (which by definition can't be dangerous
as they run in the slave interpreter) and C extensions that
provides a Safe_Init entry point). For that purpose, the master's 
\fBauto_path\fR will be used to construct the slave access path. 
In order that the slave successfully loads the Tcl library files
(which includes the auto-loading mechanism itself) the \fBtcl_library\fR will be
added or moved to the first position if necessary, in the 
slave access path, so the slave
\fBtcl_library\fR will be the same as the master's (its real
path will still be invisible to the slave though). 
In order that auto-loading works the same for the slave and
the master in this by default case, the first-level
sub directories of each directory in the master \fBauto_path\fR will
also be added (if not already included) to the slave access path.
You can always specify a more
restrictive path for which sub directories will never be searched by 
explicitly specifying your directory list with the \fB\-accessPath\fR flag
instead of relying on this default mechanism.
.PP
When the \fIaccessPath\fR is changed after the first creation or
initialization (i.e. through \fBinterpConfigure -accessPath \fR\fIlist\fR),
an \fBauto_reset\fR is automatically evaluated in the safe interpreter
to synchronize its \fBauto_index\fR with the new token list.

.SH "SEE ALSO"
interp(n), library(n), load(n), package(n), source(n), unknown(n)
 
.SH KEYWORDS
alias, auto\-loading, auto_mkindex, load, master interpreter, safe
interpreter, slave interpreter, source
'\"
'\" Copyright (c) 1990-1992 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: update.n,v 1.4.18.1 2004/10/27 14:43:15 dkf Exp $
'\" 
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
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'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
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'\"	name are examples of largest possible arguments that will be passed
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'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
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'\"	End of list of standard options for a Tk widget.
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'\"	Print arg1 underlined, then print arg2 normally.
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.AS Tcl_Interp Tcl_CreateInterp in/out
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