scan man page on MacOSX

Man page or keyword search:  
man Server   23457 pages
apropos Keyword Search (all sections)
Output format
MacOSX logo
[printable version]

scan(n)			     Tcl Built-In Commands		       scan(n)

______________________________________________________________________________

NAME
       scan - Parse string using conversion specifiers in the style of sscanf

SYNOPSIS
       scan string format ?varName varName ...?
_________________________________________________________________

INTRODUCTION
       This  command parses substrings from an input string in a fashion simi‐
       lar to the ANSI C sscanf procedure and returns a count of the number of
       conversions  performed, or -1 if the end of the input string is reached
       before any conversions have been performed.  String gives the input  to
       be  parsed  and	format	indicates  how to parse it, using % conversion
       specifiers as in sscanf.	 Each varName gives the name  of  a  variable;
       when a substring is scanned from string that matches a conversion spec‐
       ifier, the substring is assigned to the corresponding variable.	If  no
       varName	variables  are specified, then scan works in an inline manner,
       returning the data that would otherwise be stored in the variables as a
       list.   In the inline case, an empty string is returned when the end of
       the input string is reached before any conversions have been performed.

DETAILS ON SCANNING
       Scan operates by scanning string and  format  together.	 If  the  next
       character  in  format  is  a blank or tab then it matches any number of
       white space characters in string (including zero).  Otherwise, if it is
       not  a  %  character  then  it must match the next character of string.
       When a % is encountered in format, it indicates the start of a  conver‐
       sion  specifier.	  A  conversion	 specifier  contains up to four fields
       after the %: a XPG3 position specifier (or a *  to  indicate  the  con‐
       verted value is to be discarded instead of assigned to any variable); a
       number indicating a maximum substring width; a  size  modifier;	and  a
       conversion  character.  All of these fields are optional except for the
       conversion character.  The fields that are present must appear  in  the
       order given above.

       When  scan  finds  a conversion specifier in format, it first skips any
       white-space characters in string (unless the conversion character is  [
       or  c).	 Then  it  converts the next input characters according to the
       conversion specifier and stores the result in the variable given by the
       next argument to scan.

   OPTIONAL POSITIONAL SPECIFIER
       If  the	%  is followed by a decimal number and a $, as in “%2$d”, then
       the variable to use is not taken from  the  next	 sequential  argument.
       Instead, it is taken from the argument indicated by the number, where 1
       corresponds to the first varName.  If there are any  positional	speci‐
       fiers  in  format then all of the specifiers must be positional.	 Every
       varName on the argument list must correspond to exactly one  conversion
       specifier or an error is generated, or in the inline case, any position
       can be specified at most once and the empty positions will be filled in
       with empty strings.

   OPTIONAL SIZE MODIFIER
       The size modifier field is used only when scanning a substring into one
       of Tcl's integer values.	 The size modifier field dictates the  integer
       range  acceptable  to be stored in a variable, or, for the inline case,
       in a position in the result list.  The syntactically valid  values  for
       the  size  modifier  are h, L, l, and ll.  The h size modifier value is
       equivalent to the absence of a size  modifier  in  the  the  conversion
       specifier.  Either one indicates the integer range to be stored is lim‐
       ited to the same range produced by the int() function of the expr  com‐
       mand.  The L size modifier is equivalent to the l size modifier. Either
       one indicates the integer range to be stored is	limited	 to  the  same
       range produced by the wide() function of the expr command.  The ll size
       modifier indicates that the integer range to be stored is unlimited.

   MANDATORY CONVERSION CHARACTER
       The following conversion characters are supported:

       d      The input substring must be a decimal integer.  It  is  read  in
	      and  the	integer	 value is stored in the variable, truncated as
	      required by the size modifier value.

       o      The input substring must be an octal integer. It is read in  and
	      the  integer  value  is  stored  in  the	variable, truncated as
	      required by the size modifier value.

       x      The input substring must be a hexadecimal integer.  It  is  read
	      in and the integer value is stored in the variable, truncated as
	      required by the size modifier value.

       b      The input substring must be a binary integer.  It is read in and
	      the  integer  value  is  stored  in  the	variable, truncated as
	      required by the size modifier value.

       u      The input substring must be  a  decimal  integer.	  The  integer
	      value  is	 truncated as required by the size modifier value, and
	      the corresponding unsigned value for  that  truncated  range  is
	      computed	and  stored  in the variable as a decimal string.  The
	      conversion makes no sense	 without  reference  to	 a  truncation
	      range,  so  the size modifier ll is not permitted in combination
	      with conversion character u.

       i      The input substring must be an integer.  The base (i.e. decimal,
	      binary, octal, or hexadecimal) is determined in the same fashion
	      as described in expr.  The integer value is stored in the	 vari‐
	      able, truncated as required by the size modifier value.

       c      A single character is read in and its Unicode value is stored in
	      the variable as an integer value.	 Initial white	space  is  not
	      skipped  in  this	 case,	so the input substring may be a white-
	      space character.

       s      The input substring consists of all the  characters  up  to  the
	      next  white-space	 character;  the  characters are copied to the
	      variable.

       e or f or g
	      The input substring must be a floating-point  number  consisting
	      of  an  optional	sign, a string of decimal digits possibly con‐
	      taining a decimal point, and an optional exponent consisting  of
	      an  e  or E followed by an optional sign and a string of decimal
	      digits.  It is read in and stored in the variable as a floating-
	      point value.

       [chars]
	      The input substring consists of one or more characters in chars.
	      The matching string is stored in the  variable.	If  the	 first
	      character between the brackets is a ] then it is treated as part
	      of chars rather than the closing bracket for the set.  If	 chars
	      contains a sequence of the form a-b then any character between a
	      and b (inclusive) will match.  If the first  or  last  character
	      between the brackets is a -, then it is treated as part of chars
	      rather than indicating a range.

       [^chars]
	      The input substring consists of one or more  characters  not  in
	      chars.   The  matching string is stored in the variable.	If the
	      character immediately following the ^ is a ] then it is  treated
	      as  part of the set rather than the closing bracket for the set.
	      If chars contains a sequence of the form a-b then any  character
	      between  a  and b (inclusive) will be excluded from the set.  If
	      the first or last character between the brackets is a -, then it
	      is  treated  as  part  of	 chars	rather than indicating a range
	      value.

       n      No input is consumed from the input string.  Instead, the	 total
	      number  of  characters  scanned  from the input string so far is
	      stored in the variable.

       The number of characters read from the input for a  conversion  is  the
       largest	number	that  makes sense for that particular conversion (e.g.
       as many decimal digits as possible for %d, as many octal digits as pos‐
       sible  for  %o, and so on).  The input substring for a given conversion
       terminates either when a white-space character is encountered  or  when
       the  maximum  substring	width has been reached, whichever comes first.
       If a * is present in the	 conversion  specifier	then  no  variable  is
       assigned and the next scan argument is not consumed.

DIFFERENCES FROM ANSI SSCANF
       The  behavior  of  the  scan command is the same as the behavior of the
       ANSI C sscanf procedure except for the following differences:

       [1]    %p conversion specifier is not supported.

       [2]    For %c conversions a single character value is  converted	 to  a
	      decimal string, which is then assigned to the corresponding var‐
	      Name; no substring width may be specified for this conversion.

       [3]    The h modifier is always ignored and the l and L	modifiers  are
	      ignored  when  converting	 real values (i.e. type double is used
	      for the internal representation).	 The ll modifier has no sscanf
	      counterpart.

       [4]    If the end of the input string is reached before any conversions
	      have been performed and no variables are given, an empty	string
	      is returned.

EXAMPLES
       Convert a UNICODE character to its numeric value:

	      set char "x"
	      set value [scan $char %c]

       Parse  a simple color specification of the form #RRGGBB using hexadeci‐
       mal conversions with substring sizes:

	      set string "#08D03F"
	      scan $string "#%2x%2x%2x" r g b

       Parse a HH:MM time string, noting that this avoids problems with	 octal
       numbers	by  forcing interpretation as decimals (if we did not care, we
       would use the %i conversion instead):

	      set string "08:08"   ;# *Not* octal!
	      if {[scan $string "%d:%d" hours minutes] != 2} {
		  error "not a valid time string"
	      }
	      # We have to understand numeric ranges ourselves...
	      if {$minutes < 0 || $minutes > 59} {
		  error "invalid number of minutes"
	      }

       Break a string up into sequences of non-whitespace characters (note the
       use  of	the  %n conversion so that we get skipping over leading white‐
       space correct):

	      set string " a string {with braced words} + leading space "
	      set words {}
	      while {[scan $string %s%n word length] == 2} {
		  lappend words $word
		  set string [string range $string $length end]
	      }

       Parse a simple coordinate string, checking that it is complete by look‐
       ing for the terminating character explicitly:

	      set string "(5.2,-4e-2)"
	      # Note that the spaces before the literal parts of
	      # the scan pattern are significant, and that ")" is
	      # the Unicode character \u0029
	      if {
		  [scan $string " (%f ,%f %c" x y last] != 3
		  || $last != 0x0029
	      } then {
		  error "invalid coordinate string"
	      }
	      puts "X=$x, Y=$y"

       An  interactive	session demonstrating the truncation of integer values
       determined by size modifiers:

	      % set tcl_platform(wordSize)
	      4
	      % scan 20000000000000000000 %d
	      2147483647
	      % scan 20000000000000000000 %ld
	      9223372036854775807
	      % scan 20000000000000000000 %lld
	      20000000000000000000

SEE ALSO
       format(n), sscanf(3)

KEYWORDS
       conversion specifier, parse, scan

Tcl				      8.4			       scan(n)
[top]

List of man pages available for MacOSX

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net