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

______________________________________________________________________________

NAME
       string -	Manipulate strings

SYNOPSIS
       string option arg ?arg ...?
______________________________________________________________________________

DESCRIPTION
       Performs	 one  of  several string operations, depending on option.  The
       legal options (which may	be abbreviated)	are:

       string compare ?-nocase?	?-length int? string1 string2
	      Perform a	character-by-character comparison of  strings  string1
	      and  string2.  Returns -1, 0, or 1, depending on whether string1
	      is lexicographically  less  than,	 equal	to,  or	 greater  than
	      string2.	 If  -length  is specified, then only the first	length
	      characters are used in the comparison.  If -length is  negative,
	      it  is  ignored.	 If -nocase is specified, then the strings are
	      compared in a case-insensitive manner.

       string equal ?-nocase? ?-length int? string1 string2
	      Perform a	character-by-character comparison of  strings  string1
	      and string2.  Returns 1 if string1 and string2 are identical, or
	      0	when not.  If -length is specified, then only the first	length
	      characters  are used in the comparison.  If -length is negative,
	      it is ignored.  If -nocase is specified, then  the  strings  are
	      compared in a case-insensitive manner.

       string first needleString haystackString	?startIndex?
	      Search  haystackString for a sequence of characters that exactly
	      match the	characters in needleString.  If	found, return the  in-
	      dex  of  the  first  character  in  the  first such match	within
	      haystackString.  If not found,  return  -1.   If	startIndex  is
	      specified	 (in  any  of the forms	accepted by the	index method),
	      then the search is constrained to	start with  the	 character  in
	      haystackString specified by the index.  For example,
		     string first a 0a23456789abcdef 5
	      will return 10, but
		     string first a 0123456789abcdef 11
	      will return -1.

       string index string charIndex
	      Returns  the  charIndex'th  character of the string argument.  A
	      charIndex	of 0 corresponds to the	first character	of the string.
	      charIndex	may be specified as follows:			       |

	      integer							       |
			For  any  index	 value	that  passes string is integer |
			-strict, the char specified  at	 this  integral	 index |
			(e.g. 2	would refer to the "c" in "abcd").	       |

	      end							       |
			The  last  char	of the string (e.g. end	would refer to |
			the "d"	in "abcd").				       |

	      end-N							       |
			The last char of the string minus the specified	 inte- |
			ger  offset  N	(e.g.  end-1 would refer to the	"c" in |
			"abcd").					       |

	      end+N							       |
			The last char of the string plus the specified integer |
			offset	N  (e.g.  end+-1  would	 refer	to  the	"c" in |
			"abcd").					       |

	      M+N							       |
			The char specified at the integral index that  is  the |
			sum of integer values M	and N (e.g. 1+1	would refer to |
			the "c"	in "abcd").				       |

	      M-N							       |
			The char specified at the integral index that  is  the |
			difference  of	integer	values M and N (e.g. 2-1 would |
			refer to the "b" in "abcd").			       |

	      In the specifications above, the integer	value  M  contains  no |
	      trailing	whitespace and the integer value N contains no leading |
	      whitespace.						       |

	      If charIndex is less than	0 or greater  than  or	equal  to  the |
	      length of	the string then	this command returns an	empty string.  |

       string is class ?-strict? ?-failindex varname? string
	      Returns 1	if string is a valid member of the specified character
	      class, otherwise returns 0.  If -strict is  specified,  then  an
	      empty  string returns 0, otherwise an empty string will return 1
	      on any class.  If	-failindex is specified, then if the  function
	      returns 0, the index in the string where the class was no	longer
	      valid will be stored in the variable named varname.  The varname
	      will not be set if string	is returns 1.  The following character
	      classes are recognized (the class	name can be abbreviated):

	      alnum	  Any Unicode alphabet or digit	character.

	      alpha	  Any Unicode alphabet character.

	      ascii	  Any character	with a value less than	\u0080	(those
			  that are in the 7-bit	ascii range).

	      boolean	  Any of the forms allowed to Tcl_GetBoolean.

	      control	  Any Unicode control character.

	      digit	  Any  Unicode	digit  character.   Note that this in-
			  cludes characters outside of the [0-9] range.

	      double	  Any of the valid forms for a double in Tcl, with op-
			  tional  surrounding  whitespace.   In	 case  of  un-
			  der/overflow in the value, 0	is  returned  and  the
			  varname will contain -1.

	      false	  Any of the forms allowed to Tcl_GetBoolean where the
			  value	is false.

	      graph	  Any Unicode printing character, except space.

	      integer	  Any of the valid string formats for a	32-bit integer
			  value	 in Tcl, with optional surrounding whitespace.
			  In case of under/overflow in the  value,  0  is  re-
			  turned and the varname will contain -1.

	      list	  Any proper list structure, with optional surrounding
			  whitespace. In case of improper list structure, 0 is
			  returned  and	 the varname will contain the index of
			  the "element"	where the list parsing fails, or -1 if
			  this cannot be determined.

	      lower	  Any Unicode lower case alphabet character.

	      print	  Any Unicode printing character, including space.

	      punct	  Any Unicode punctuation character.

	      space	  Any  Unicode whitespace character or mongolian vowel
			  separator (U+180e), but not NEL/Next Line (U+0085).

	      true	  Any of the forms allowed to Tcl_GetBoolean where the
			  value	is true.

	      upper	  Any  upper  case  alphabet  character	in the Unicode
			  character set.				       |

	      wideinteger						       |
			  Any of the valid forms for a wide  integer  in  Tcl, |
			  with	optional  surrounding  whitespace.  In case of |
			  under/overflow in the	value, 0 is returned  and  the |
			  varname will contain -1.

	      wordchar	  Any  Unicode	word  character.  That is any alphanu-
			  meric	character, and any Unicode connector  punctua-
			  tion characters (e.g.	underscore).

	      xdigit	  Any hexadecimal digit	character ([0-9A-Fa-f]).

	      In the case of boolean, true and false, if the function will re-
	      turn 0, then the varname will always be set to  0,  due  to  the
	      varied nature of a valid boolean value.

       string last needleString	haystackString ?lastIndex?
	      Search  haystackString for a sequence of characters that exactly
	      match the	characters in needleString.  If	found, return the  in-
	      dex  of  the  first  character  in  the  last  such match	within
	      haystackString.  If there	is  no	match,	then  return  -1.   If
	      lastIndex	 is specified (in any of the forms accepted by the in-
	      dex method), then	only the characters in	haystackString	at  or
	      before the specified lastIndex will be considered	by the search.
	      For example,
		     string last a 0a23456789abcdef 15
	      will return 10, but
		     string last a 0a23456789abcdef 9
	      will return 1.

       string length string
	      Returns a	decimal	string giving  the  number  of	characters  in
	      string.	Note that this is not necessarily the same as the num-
	      ber of bytes used	to store the  string.	If  the	 object	 is  a
	      ByteArray	 object	 (such as those	returned from reading a	binary
	      encoded channel),	then this will return the actual  byte	length
	      of the object.

       string map ?-nocase? mapping string
	      Replaces	substrings  in	string based on	the key-value pairs in
	      mapping.	mapping	is a list of key value key value  ...	as  in
	      the  form	 returned by array get.	 Each instance of a key	in the
	      string will be replaced with its corresponding value.   If  -no-
	      case  is specified, then matching	is done	without	regard to case
	      differences. Both	key and	value may be multiple characters.  Re-
	      placement	 is  done  in  an ordered manner, so the key appearing
	      first in the list	will be	checked	first, and so on.   string  is
	      only  iterated  over once, so earlier key	replacements will have
	      no affect	for later key matches.	For example,
		     string map	{abc 1 ab 2 a 3	1 0} 1abcaababcabababc
	      will return the string 01321221.

	      Note that	if an earlier key is a prefix of a later one, it  will
	      completely  mask	the  later one.	 So if the previous example is
	      reordered	like this,
		     string map	{1 0 ab	2 a 3 abc 1} 1abcaababcabababc
	      it will return the string	02c322c222c.

       string match ?-nocase? pattern string
	      See if pattern matches string; return 1 if it does, 0 if it does
	      not.   If	 -nocase  is  specified,  then the pattern attempts to
	      match against the	string in a case insensitive manner.  For  the
	      two  strings  to	match, their contents must be identical	except
	      that the following special sequences may appear in pattern:

	      *		Matches	any sequence of	characters in string,  includ-
			ing a null string.

	      ?		Matches	any single character in	string.

	      [chars]	Matches	any character in the set given by chars.  If a
			sequence of the	form x-y appears in  chars,  then  any
			character  between  x  and  y,	inclusive, will	match.
			When used with -nocase,	the end	points	of  the	 range
			are  converted	to  lower case first.  Whereas {[A-z]}
			matches	"_" when matching case-sensitively (since  "_"
			falls  between	the "Z"	and "a"), with -nocase this is
			considered like	 {[A-Za-z]}  (and  probably  what  was
			meant in the first place).

	      \x	Matches	 the  single character x.  This	provides a way
			of avoiding the	special	interpretation of the  charac-
			ters *?[]\ in pattern.

       string range string first last
	      Returns  a range of consecutive characters from string, starting
	      with the character whose index is	 first	and  ending  with  the
	      character	whose index is last. An	index of 0 refers to the first
	      character	of the string.	first and last may be specified	as for
	      the index	method.	 If first is less than zero then it is treated
	      as if it were zero, and if last is greater than or equal to  the
	      length  of  the string then it is	treated	as if it were end.  If
	      first is greater than last then an empty string is returned.

       string repeat string count
	      Returns string repeated count number of times.

       string replace string first last	?newstring?
	      Removes a	range of consecutive characters	from string,  starting
	      with  the	 character  whose  index  is first and ending with the
	      character	whose index is last.  An index	of  0  refers  to  the
	      first  character of the string.  First and last may be specified
	      as for the index method.	If newstring is	specified, then	it  is
	      placed  in  the  removed character range.	 If first is less than
	      zero then	it is treated as if it	were  zero,  and  if  last  is
	      greater  than  or	 equal	to the length of the string then it is
	      treated as if it were end.  If first is greater than last	or the
	      length  of  the initial string, or last is less than 0, then the
	      initial string is	returned untouched.			       |

       string reverse string						       |
	      Returns a	string that is the same	length as string but with  its |
	      characters in the	reverse	order.

       string tolower string ?first? ?last?
	      Returns a	value equal to string except that all upper (or	title)
	      case letters have	been converted to lower	 case.	 If  first  is
	      specified,  it  refers  to the first char	index in the string to
	      start modifying.	If last	is specified, it refers	 to  the  char
	      index  in	the string to stop at (inclusive).  first and last may
	      be specified as for the index method.

       string totitle string ?first? ?last?
	      Returns a	value equal to string except that the first  character
	      in string	is converted to	its Unicode title case variant (or up-
	      per case if there	is no title case variant) and the rest of  the
	      string  is  converted  to	lower case.  If	first is specified, it
	      refers to	the first char index in	the string to start modifying.
	      If  last is specified, it	refers to the char index in the	string
	      to stop at (inclusive).  first and last may be specified as  for
	      the index	method.

       string toupper string ?first? ?last?
	      Returns a	value equal to string except that all lower (or	title)
	      case letters have	been converted to upper	 case.	 If  first  is
	      specified,  it  refers  to the first char	index in the string to
	      start modifying.	If last	is specified, it refers	 to  the  char
	      index  in	the string to stop at (inclusive).  first and last may
	      be specified as for the index method.

       string trim string ?chars?
	      Returns a	value equal to	string	except	that  any  leading  or
	      trailing characters present in the string	given by chars are re-
	      moved.  If chars is not specified	then white  space  is  removed
	      (spaces, tabs, newlines, and carriage returns).

       string trimleft string ?chars?
	      Returns  a value equal to	string except that any leading charac-
	      ters present in the string given by chars	are removed.  If chars
	      is not specified then white space	is removed (spaces, tabs, new-
	      lines, and carriage returns).

       string trimright	string ?chars?
	      Returns a	value equal to string except that any trailing charac-
	      ters present in the string given by chars	are removed.  If chars
	      is not specified then white space	is removed (spaces, tabs, new-
	      lines, and carriage returns).

OBSOLETE SUBCOMMANDS
       These subcommands are currently supported, but are likely to go away in
       a future	release	as their functionality is either virtually never  used
       or highly misleading.

       string bytelength string
	      Returns a	decimal	string giving the number of bytes used to rep-
	      resent string in memory.	Because	UTF-8 uses one to three	 bytes
	      to represent Unicode characters, the byte	length will not	be the
	      same as the character length in  general.	  The  cases  where  a
	      script  cares  about  the	 byte  length are rare.	 In almost all
	      cases, you should	use the	string length operation	(including de-
	      termining	 the  length of	a Tcl ByteArray	object).  Refer	to the
	      Tcl_NumUtfChars manual entry for more details on the UTF-8  rep-
	      resentation.

       string wordend string charIndex
	      Returns  the  index  of the character just after the last	one in
	      the word containing character charIndex  of  string.   charIndex
	      may  be specified	as for the index method.  A word is considered
	      to be any	contiguous range of alphanumeric (Unicode  letters  or
	      decimal  digits)	or  underscore (Unicode	connector punctuation)
	      characters, or any single	character other	than these.

       string wordstart	string charIndex
	      Returns the index	of the first character in the word  containing
	      character	 charIndex  of	string.	 charIndex may be specified as
	      for the index method.  A word is considered to be	any contiguous
	      range of alphanumeric (Unicode letters or	decimal	digits)	or un-
	      derscore (Unicode	connector punctuation) characters, or any sin-
	      gle character other than these.

EXAMPLE
       Test  if	the string in the variable string is a proper non-empty	prefix
       of the string foobar.
	      set length [string length	$string]
	      if {$length == 0}	{
		  set isPrefix 0
	      }	else {
		  set isPrefix [string equal -length $length $string "foobar"]
	      }

SEE ALSO
       expr(n),	list(n)

KEYWORDS
       case conversion,	compare, index,	match, pattern,	string,	 word,	equal,
       ctype, character, reverse

Tcl				      8.1			     string(n)

NAME | SYNOPSIS | DESCRIPTION | OBSOLETE SUBCOMMANDS | EXAMPLE | SEE ALSO | KEYWORDS

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