Go to main content

man pages section 1: User Commands

Exit Print View

Updated: Wednesday, February 10, 2021
 
 

binary (1t)

Name

binary - Insert and extract fields from binary strings

Synopsis

binary decode format ?-option value ...? data                           |
binary encode format ?-option value ...? data                           |
binary format formatString ?arg arg ...?
binary scan string formatString ?varName varName ...?

Description

binary(1t)                   Tcl Built-In Commands                  binary(1t)



______________________________________________________________________________

NAME
       binary - Insert and extract fields from binary strings

SYNOPSIS
       binary decode format ?-option value ...? data                           |
       binary encode format ?-option value ...? data                           |
       binary format formatString ?arg arg ...?
       binary scan string formatString ?varName varName ...?
______________________________________________________________________________

DESCRIPTION
       This  command  provides  facilities  for manipulating binary data.  The
       subcommand binary format creates a binary string from normal  Tcl  val-
       ues.   For  example,  given the values 16 and 22, on a 32-bit architec-
       ture, it might produce an 8-byte binary string consisting of two 4-byte
       integers,  one  for  each  of the numbers.  The subcommand binary scan,
       does the opposite: it extracts data from a binary string and returns it
       as  ordinary  Tcl  string  values.  The binary encode and binary decode |
       subcommands convert binary data to or from  string  encodings  such  as |
       base64 (used in MIME messages for example).

       Note that other operations on binary data, such as taking a subsequence
       of it, getting its length, or reinterpreting it as  a  string  in  some
       encoding,  are  done  by other Tcl commands (respectively string range,
       string length and encoding convertfrom in the example cases).  A binary
       string in Tcl is merely one where all the characters it contains are in
       the range \u0000-\u00FF.

BINARY ENCODE AND DECODE
       When encoding binary data as a readable  string,  the  starting  binary |
       data  is passed to the binary encode command, together with the name of |
       the encoding to use and any  encoding-specific  options  desired.  Data |
       which  has  been  encoded  can  be  converted back to binary form using |
       binary decode. The following formats and options are supported.         |

       base64                                                                  |
              The base64 binary encoding is commonly used in mail messages and |
              XML  documents, and uses mostly upper and lower case letters and |
              digits. It has the distinction of being  able  to  be  rewrapped |
              arbitrarily without losing information.                          |

              During encoding, the following options are supported:            |

              -maxlen length                                                   |
                     Indicates  that  the output should be split into lines of |
                     no more than length characters. By default, lines are not |
                     split.                                                    |

              -wrapchar character                                              |
                     Indicates  that,  when  lines  are  split  because of the |
                     -maxlen option, character  should  be  used  to  separate |
                     lines. By default, this is a newline character, "\n".     |

              During decoding, the following options are supported:            |

              -strict                                                          |
                     Instructs  the decoder to throw an error if it encounters |
                     whitespace characters. Otherwise it ignores them.         |

       hex                                                                     |
              The hex binary encoding converts each byte to a pair of hexadec- |
              imal digits in big-endian form.                                  |

              No  options  are supported during encoding. During decoding, the |
              following options are supported:                                 |

              -strict                                                          |
                     Instructs the decoder to throw an error if it  encounters |
                     whitespace characters. Otherwise it ignores them.         |

       uuencode                                                                |
              The  uuencode  binary encoding used to be common for transfer of |
              data between Unix systems and on  USENET,  but  is  less  common |
              these  days, having been largely superseded by the base64 binary |
              encoding.                                                        |

              During encoding, the following  options  are  supported  (though |
              changing  them  may  produce files that other implementations of |
              decoders cannot process):                                        |

              -maxlen length                                                   |
                     Indicates that the output should be split into  lines  of |
                     no  more  than  length  characters. By default, lines are |
                     split every 61 characters, and this must be in the  range |
                     3 to 85 due to limitations in the encoding.               |

              -wrapchar character                                              |
                     Indicates  that,  when  lines  are  split  because of the |
                     -maxlen option, character  should  be  used  to  separate |
                     lines. By default, this is a newline character, "\n".     |

              During decoding, the following options are supported:            |

              -strict                                                          |
                     Instructs  the decoder to throw an error if it encounters |
                     unexpected whitespace characters.  Otherwise  it  ignores |
                     them.                                                     |

              Note  that neither the encoder nor the decoder handle the header |
              and footer of the uuencode format.                               |

BINARY FORMAT
       The binary format command generates a binary  string  whose  layout  is
       specified  by  the  formatString and whose contents come from the addi-
       tional arguments.  The resulting binary value is returned.

       The formatString consists of a sequence of zero or  more  field  speci-
       fiers separated by zero or more spaces.  Each field specifier is a sin-
       gle type character followed by an optional flag character  followed  by
       an  optional numeric count.  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 count typically indicates how many
       items of the specified type are taken from the value.  If present,  the
       count  is a non-negative decimal integer or *, 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. The  flag  character  is
       ignored for binary format.

       Here is a small example to clarify the relation between the field spec-
       ifiers and the arguments:
              binary format d3d {1.0 2.0 3.0 4.0} 0.1

       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  speci-
       fier.  The  resulting binary string contains the four numbers 1.0, 2.0,
       3.0 and 0.1.

       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:

       a    Stores a byte string of length count in the output string.   Every
            character is taken as modulo 256 (i.e. the low byte of every char-
            acter is used, and the high byte discarded) so when storing  char-
            acter   strings   not  wholly  expressible  using  the  characters
            \u0000-\u00ff, the encoding convertto command should be used first
            to change the string into an external representation if this trun-
            cation is not desired (i.e. if the characters are not part of  the
            ISO  8859-1  character  set.)   If arg has fewer than count bytes,
            then additional zero bytes are used to pad out the field.  If  arg
            is  longer than the specified length, the extra characters will be
            ignored.  If count is *, then all of the bytes in arg will be for-
            matted.   If  count is omitted, then one character will be format-
            ted.  For example,
                   binary format a7a*a alpha bravo charlie
            will return a string equivalent to alpha\000\000bravoc,
                   binary format a* [encoding convertto utf-8 \u20ac]
            will return a string equivalent  to  \342\202\254  (which  is  the
            UTF-8 byte sequence for a Euro-currency character) and
                   binary format a* [encoding convertto iso8859-15 \u20ac]
            will  return a string equivalent to \244 (which is the ISO 8859-15
            byte sequence for a Euro-currency character). Contrast these  last
            two with:
                   binary format a* \u20ac
            which  returns a string equivalent to \254 (i.e. \xac) by truncat-
            ing the high-bits of the character, and which is probably not what
            is desired.

       A    This form is the same as a except that spaces are used for padding
            instead of nulls.  For example,
                   binary format A6A*A alpha bravo charlie
            will return alpha bravoc.

       b    Stores a string of count binary digits in low-to-high order within
            each  byte in the output string.  Arg must contain a sequence of 1
            and 0 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 arg has fewer than count digits, then  zeros
            will  be  used  for  the remaining bits.  If arg has more than the
            specified number of digits, the extra digits will be ignored.   If
            count  is  *, then all of the digits in arg will be formatted.  If
            count 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,
                   binary format b5b* 11100 111000011010
            will return a string equivalent to \x07\x87\x05.

       B    This form is the same as b except that  the  bits  are  stored  in
            high-to-low order within each byte.  For example,
                   binary format B5B* 11100 111000011010
            will return a string equivalent to \xe0\xe1\xa0.

       H    Stores  a string of count hexadecimal digits in high-to-low within
            each byte in the output string.  Arg 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 high-to-low order within each byte.  If arg has fewer
            than count digits, then zeros will be used for the remaining  dig-
            its.   If  arg  has  more than the specified number of digits, the
            extra digits will be ignored.  If count is *, then all of the dig-
            its in arg will be formatted.  If count 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,
                   binary format H3H*H2 ab DEF 987
            will return a string equivalent to \xab\x00\xde\xf0\x98.

       h    This form is the same as H except that the digits  are  stored  in
            low-to-high  order  within each byte. This is seldom required. For
            example,
                   binary format h3h*h2 AB def 987
            will return a string equivalent to \xba\x00\xed\x0f\x89.

       c    Stores one or more 8-bit integer values in the output string.   If
            no  count is specified, then arg must consist of an integer value.
            If count is specified, arg must consist of a  list  containing  at
            least that many integers. The low-order 8 bits of each integer are
            stored as a one-byte value at the cursor position.  If count is *,
            then  all of the integers in the list are formatted. If the number
            of elements in the list is greater than count, then the extra ele-
            ments are ignored.  For example,
                   binary format c3cc* {3 -3 128 1} 260 {2 5}
            will  return  a  string  equivalent  to  \x03\xfd\x80\x04\x02\x05,
            whereas
                   binary format c {2 5}
            will generate an error.

       s    This form is the same as c 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  at  the  cursor  position  with  the least significant byte
            stored first.  For example,
                   binary format s3 {3 -3 258 1}
            will return a string equivalent to \x03\x00\xfd\xff\x02\x01.

       S    This form is the same as s except  that  it  stores  one  or  more
            16-bit  integers  in  big-endian  byte order in the output string.
            For example,
                   binary format S3 {3 -3 258 1}
            will return a string equivalent to \x00\x03\xff\xfd\x01\x02.

       t    This form (mnemonically tiny) is the same as s and S  except  that
            it  stores  the 16-bit integers in the output string in the native
            byte order of the machine where the Tcl  script  is  running.   To
            determine  what  the native byte order of the machine is, refer to
            the byteOrder element of the tcl_platform array.

       i    This form is the same as c 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,
                   binary format i3 {3 -3 65536 1}
            will       return       a       string        equivalent        to
            \x03\x00\x00\x00\xfd\xff\xff\xff\x00\x00\x01\x00

       I    This  form  is the same as i except that it stores one or more one
            or more 32-bit integers in big-endian byte  order  in  the  output
            string.  For example,
                   binary format I3 {3 -3 65536 1}
            will        return        a       string       equivalent       to
            \x00\x00\x00\x03\xff\xff\xff\xfd\x00\x01\x00\x00

       n    This form (mnemonically number or normal) is the same as i  and  I
            except  that it stores the 32-bit integers in the output string in
            the native byte order of the machine where the Tcl script is  run-
            ning.   To determine what the native byte order of the machine is,
            refer to the byteOrder element of the tcl_platform array.

       w    This form is the same as c 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,
                   binary format w 7810179016327718216
            will return the string HelloTcl

       W    This form is the same as w except that it stores one or  more  one
            or  more  64-bit  integers  in big-endian byte order in the output
            string.  For example,
                   binary format Wc 4785469626960341345 110
            will return the string BigEndian

       m    This form (mnemonically the mirror of w) is the same as  w  and  W
            except  that it stores the 64-bit integers in the output string in
            the native byte order of the machine where the Tcl script is  run-
            ning.   To determine what the native byte order of the machine is,
            refer to the byteOrder element of the tcl_platform array.

       f    This form is the same as c except that it stores one or  more  one
            or  more  single-precision floating point numbers 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  over-
            flows  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-preci-
            sion.   For  example, on a Windows system running on an Intel Pen-
            tium processor,
                   binary format f2 {1.6 3.4}
            will       return       a       string        equivalent        to
            \xcd\xcc\xcc\x3f\x9a\x99\x59\x40.

       r    This  form  (mnemonically  real)  is  the same as f except that it
            stores the single-precision  floating  point  numbers  in  little-
            endian  order.   This  conversion  only produces meaningful output
            when used on machines which use the IEEE floating point  represen-
            tation (very common, but not universal.)

       R    This form is the same as r except that it stores the single-preci-
            sion floating point numbers in big-endian order.

       d    This form is the same as f except that it stores one or  more  one
            or  more  double-precision floating point numbers in the machine's
            native representation in the output string.   For  example,  on  a
            Windows system running on an Intel Pentium processor,
                   binary format d1 {1.6}
            will        return        a       string       equivalent       to
            \x9a\x99\x99\x99\x99\x99\xf9\x3f.

       q    This form (mnemonically the mirror of d) is the same as  d  except
            that it stores the double-precision floating point numbers in lit-
            tle-endian order.  This conversion only produces meaningful output
            when  used on machines which use the IEEE floating point represen-
            tation (very common, but not universal.)

       Q    This form is the same as q except that it stores the double-preci-
            sion floating point numbers in big-endian order.

       x    Stores  count  null  bytes  in the output string.  If count is not
            specified, stores one null byte.  If  count  is  *,  generates  an
            error.  This type does not consume an argument.  For example,
                   binary format a3xa3x2a3 abc def ghi
            will return a string equivalent to abc\000def\000\000ghi.

       X    Moves  the cursor back count bytes in the output string.  If count
            is * or is larger than the current cursor position, then the  cur-
            sor  is positioned at location 0 so that the next byte stored will
            be the first byte in the result string.  If count is omitted  then
            the  cursor is moved back one byte.  This type does not consume an
            argument.  For example,
                   binary format a3X*a3X2a3 abc def ghi
            will return dghi.

       @    Moves the cursor to the absolute location  in  the  output  string
            specified  by  count.   Position 0 refers to the first byte in the
            output string.  If count 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  count is *, then the cursor is moved to the current end of the
            output string.  If count is omitted, then an error will be  gener-
            ated.  This type does not consume an argument. For example,
                   binary format a5@2a1@*a3@10a1 abcde f ghi j
            will return abfdeghi\000\000j.

BINARY SCAN
       The  binary  scan command parses fields from a binary string, returning
       the number of conversions performed.  String gives the input  bytes  to
       be  parsed (one byte per character, and characters not representable as
       a byte have their high bits chopped) and formatString indicates how  to
       parse  it.   Each varName gives the name of a variable; when a field is
       scanned from string the result is assigned to the  corresponding  vari-
       able.

       As  with binary format, the formatString 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 flag char-
       acter followed by an optional numeric  count.   Most  field  specifiers
       consume one argument to obtain the variable into which the scanned val-
       ues should be placed.  The type character specifies how the binary data
       is  to be interpreted.  The count typically indicates how many items of
       the specified type are taken from the data.  If present, the count is a
       non-negative decimal integer or *, 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 cur-
       rent field specifier, then the corresponding variable is left untouched
       and  binary  scan 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.
       The flag character "u" may be given to cause some types to be  read  as
       unsigned  values.  The  flag  is  accepted  for  all field types but is
       ignored for non-integer fields.

       A similar example as with binary format  should  explain  the  relation
       between  field specifiers and arguments in case of the binary scan sub-
       command:
              binary scan $bytes s3s first second

       This command (provided the binary string in the variable bytes is  long
       enough)  assigns  a  list  of  three integers to the variable first and
       assigns a single value to the variable second.  If bytes contains fewer
       than  8 bytes (i.e. four 2-byte integers), no assignment to second will
       be made, and if bytes contains fewer than 6 bytes  (i.e.  three  2-byte
       integers), no assignment to first will be made.  Hence:
              puts [binary scan abcdefg s3s first second]
              puts $first
              puts $second
       will print (assuming neither variable is set previously):
              1
              25185 25699 26213
              can't read "second": no such variable

       It is important to note that the c, s, and S (and i and I on 64bit sys-
       tems) will be scanned into long data size values.  In doing this,  val-
       ues  that  have  their high bit set (0x80 for chars, 0x8000 for shorts,
       0x80000000 for ints), will be sign extended.  Thus the  following  will
       occur:
              set signShort [binary format s1 0x8000]
              binary scan $signShort s1 val; # val == 0xFFFF8000
       If  you  require unsigned values you can include the "u" flag character
       following the field type. For example, to read an unsigned short value:
              set signShort [binary format s1 0x8000]
              binary scan $signShort su1 val; # val == 0x00008000

       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:

       a    The  data  is  a byte string of length count.  If count is *, then
            all of the remaining bytes in string  will  be  scanned  into  the
            variable.   If  count  is  omitted, then one byte will be scanned.
            All bytes scanned will be interpreted as being characters  in  the
            range  \u0000-\u00ff  so  the encoding convertfrom command will be
            needed if the string is not a binary string or a string encoded in
            ISO 8859-1.  For example,
                   binary scan abcde\000fghi a6a10 var1 var2
            will  return  1  with the string equivalent to abcde\000 stored in
            var1 and var2 left unmodified, and
                   binary scan \342\202\254 a* var1
                   set var2 [encoding convertfrom utf-8 $var1]
            will store a Euro-currency character in var2.

       A    This form is the same as a, except trailing blanks and  nulls  are
            stripped  from  the scanned value before it is stored in the vari-
            able.  For example,
                   binary scan "abc efghi  \000" A* var1
            will return 1 with abc efghi stored in var1.

       b    The data is turned into a string of count 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 count is  *,  then  all  of  the
            remaining  bits  in  string will be scanned.  If count is omitted,
            then one bit will be scanned.  For example,
                   binary scan \x07\x87\x05 b5b* var1 var2
            will return 2 with  11100  stored  in  var1  and  1110000110100000
            stored in var2.

       B    This  form is the same as b, except the bits are taken in high-to-
            low order within each byte.  For example,
                   binary scan \x70\x87\x05 B5B* var1 var2
            will return 2 with  01110  stored  in  var1  and  1000011100000101
            stored in var2.

       H    The  data  is  turned into a string of count hexadecimal digits in
            high-to-low 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  high-to-low  order
            within  each byte. Any extra bits in the last byte are ignored. If
            count is *, then all of the remaining hex digits in string will be
            scanned.  If count is omitted, then one hex digit will be scanned.
            For example,
                   binary scan \x07\xC6\x05\x1f\x34 H3H* var1 var2
            will return 2 with 07c stored in var1 and 051f34 stored in var2.

       h    This form is the same as H, except the digits are taken in reverse
            (low-to-high) order within each byte. For example,
                   binary scan \x07\x86\x05\x12\x34 h3h* var1 var2
            will return 2 with 706 stored in var1 and 502143 stored in var2.

            Note  that  most  code that wishes to parse the hexadecimal digits
            from multiple bytes in order should use the H format.

       c    The data is turned into count 8-bit signed integers and stored  in
            the  corresponding  variable as a list. If count is *, then all of
            the remaining bytes in string will be scanned.  If count is  omit-
            ted, then one 8-bit integer will be scanned.  For example,
                   binary scan \x07\x86\x05 c2c* var1 var2
            will  return  2  with  7 -122 stored in var1 and 5 stored in var2.
            Note that the integers returned are signed, but they can  be  con-
            verted to unsigned 8-bit quantities using an expression like:
                   set num [expr { $num & 0xff }]

       s    The  data  is  interpreted  as count 16-bit signed integers repre-
            sented in little-endian byte order.  The integers  are  stored  in
            the  corresponding variable as a list.  If count is *, then all of
            the remaining bytes in string will be scanned.  If count is  omit-
            ted, then one 16-bit integer will be scanned.  For example,
                   binary scan \x05\x00\x07\x00\xf0\xff s2s* var1 var2
            will  return  2  with  5  7 stored in var1 and -16 stored in var2.
            Note that the integers returned are signed, but they can  be  con-
            verted to unsigned 16-bit quantities using an expression like:
                   set num [expr { $num & 0xffff }]

       S    This  form is the same as s except that the data is interpreted as
            count 16-bit signed integers represented in big-endian byte order.
            For example,
                   binary scan \x00\x05\x00\x07\xff\xf0 S2S* var1 var2
            will return 2 with 5 7 stored in var1 and -16 stored in var2.

       t    The  data  is  interpreted  as count 16-bit signed integers repre-
            sented in the native byte order of the  machine  running  the  Tcl
            script.   It is otherwise identical to s and S.  To determine what
            the native byte order of the machine is, refer  to  the  byteOrder
            element of the tcl_platform array.

       i    The  data  is  interpreted  as count 32-bit signed integers repre-
            sented in little-endian byte order.  The integers  are  stored  in
            the  corresponding variable as a list.  If count is *, then all of
            the remaining bytes in string will be scanned.  If count is  omit-
            ted, then one 32-bit integer will be scanned.  For example,
                   set str \x05\x00\x00\x00\x07\x00\x00\x00\xf0\xff\xff\xff
                   binary scan $str i2i* var1 var2
            will  return  2  with  5  7 stored in var1 and -16 stored in var2.
            Note that the integers returned are signed, but they can  be  con-
            verted to unsigned 32-bit quantities using an expression like:
                   set num [expr { $num & 0xffffffff }]

       I    This  form is the same as I except that the data is interpreted as
            count 32-bit signed integers represented in big-endian byte order.
            For example,
                   set str \x00\x00\x00\x05\x00\x00\x00\x07\xff\xff\xff\xf0
                   binary scan $str I2I* var1 var2
            will return 2 with 5 7 stored in var1 and -16 stored in var2.

       n    The  data  is  interpreted  as count 32-bit signed integers repre-
            sented in the native byte order of the  machine  running  the  Tcl
            script.   It is otherwise identical to i and I.  To determine what
            the native byte order of the machine is, refer  to  the  byteOrder
            element of the tcl_platform array.

       w    The  data  is  interpreted  as count 64-bit signed integers repre-
            sented in little-endian byte order.  The integers  are  stored  in
            the  corresponding variable as a list.  If count is *, then all of
            the remaining bytes in string will be scanned.  If count is  omit-
            ted, then one 64-bit integer will be scanned.  For example,
                   set str \x05\x00\x00\x00\x07\x00\x00\x00\xf0\xff\xff\xff
                   binary scan $str wi* var1 var2
            will  return  2  with 30064771077 stored in var1 and -16 stored in
            var2.  Note that the integers returned are signed  and  cannot  be
            represented by Tcl as unsigned values.

       W    This  form is the same as w except that the data is interpreted as
            count 64-bit signed integers represented in big-endian byte order.
            For example,
                   set str \x00\x00\x00\x05\x00\x00\x00\x07\xff\xff\xff\xf0
                   binary scan $str WI* var1 var2
            will  return  2  with 21474836487 stored in var1 and -16 stored in
            var2.

       m    The data is interpreted as count  64-bit  signed  integers  repre-
            sented  in  the  native  byte order of the machine running the Tcl
            script.  It is otherwise identical to w and W.  To determine  what
            the  native  byte  order of the machine is, refer to the byteOrder
            element of the tcl_platform array.

       f    The data is interpreted as count 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  count  is *, then all of the remaining bytes in string will be
            scanned.  If count 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 depen-
            dent.   For  example, on a Windows system running on an Intel Pen-
            tium processor,
                   binary scan \x3f\xcc\xcc\xcd f var1
            will return 1 with 1.6000000238418579 stored in var1.

       r    This form is the same as f except that the data is interpreted  as
            count  single-precision  floating  point  number  in little-endian
            order.  This conversion is not portable to the minority of systems
            not using IEEE floating point representations.

       R    This  form is the same as f except that the data is interpreted as
            count single-precision floating point number in big-endian  order.
            This  conversion  is  not  portable to the minority of systems not
            using IEEE floating point representations.

       d    This form is the same as f except that the data is interpreted  as
            count  double-precision  floating  point  numbers in the machine's
            native representation. For example, on a Windows system running on
            an Intel Pentium processor,
                   binary scan \x9a\x99\x99\x99\x99\x99\xf9\x3f d var1
            will return 1 with 1.6000000000000001 stored in var1.

       q    This  form is the same as d except that the data is interpreted as
            count double-precision  floating  point  number  in  little-endian
            order.  This conversion is not portable to the minority of systems
            not using IEEE floating point representations.

       Q    This form is the same as d except that the data is interpreted  as
            count  double-precision floating point number in big-endian order.
            This conversion is not portable to the  minority  of  systems  not
            using IEEE floating point representations.

       x    Moves  the cursor forward count bytes in string.  If count is * or
            is larger than the number of bytes after the current cursor  posi-
            tion, then the cursor is positioned after the last byte in string.
            If count is omitted, then the cursor is moved  forward  one  byte.
            Note that this type does not consume an argument.  For example,
                   binary scan \x01\x02\x03\x04 x2H* var1
            will return 1 with 0304 stored in var1.

       X    Moves  the cursor back count bytes in string.  If count is * or is
            larger than the current cursor position, then the cursor is  posi-
            tioned  at  location  0  so that the next byte scanned will be the
            first byte in string.  If count is  omitted  then  the  cursor  is
            moved  back  one  byte.   Note  that this type does not consume an
            argument.  For example,
                   binary scan \x01\x02\x03\x04 c2XH* var1 var2
            will return 2 with 1 2 stored in var1 and 020304 stored in var2.

       @    Moves the cursor to the absolute location in the data string spec-
            ified  by count.  Note that position 0 refers to the first byte in
            string.  If count refers to a position beyond the end  of  string,
            then  the  cursor  is positioned after the last byte.  If count is
            omitted, then an error will be generated.  For example,
                   binary scan \x01\x02\x03\x04 c2@1H* var1 var2
            will return 2 with 1 2 stored in var1 and 020304 stored in var2.

PORTABILITY ISSUES
       The r, R, q and Q conversions will only work reliably for  transferring
       data  between  computers which are all using IEEE floating point repre-
       sentations.  This is very  common,  but  not  universal.   To  transfer
       floating-point  numbers  portably  between all architectures, use their
       textual representation (as produced by format) instead.

EXAMPLES
       This is a procedure to write a Tcl string to a  binary-encoded  channel
       as UTF-8 data preceded by a length word:

              proc writeString {channel string} {
                  set data [encoding convertto utf-8 $string]
                  puts -nonewline [binary format Ia* \
                          [string length $data] $data]
              }

       This  procedure  reads  a string from a channel that was written by the
       previously presented writeString procedure:

              proc readString {channel} {
                  if {![binary scan [read $channel 4] I length]} {
                      error "missing length"
                  }
                  set data [read $channel $length]
                  return [encoding convertfrom utf-8 $data]
              }

       This converts the contents of a file (named in the  variable  filename)
       to base64 and prints them:

              set f [open $filename rb]
              set data [read $f]
              close $f
              puts [binary encode base64 -maxlen 64 $data]


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | runtime/tcl-8    |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       encoding(n), format(n), scan(n), string(n), tcl_platform(n)

KEYWORDS
       binary, format, scan



NOTES
       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source was downloaded from  http://prdownloads.sourceforge.net/tcl/tcl-
       core8.6.7-src.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcl.tk/.



Tcl                                   8.0                           binary(1t)