Provided by: tcl8.6-doc_8.6.12+dfsg-1build1_all 
NAME
string - Manipulate strings
SYNOPSIS
string option arg ?arg ...?
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DESCRIPTION
Performs one of several string operations, depending on option. The legal options (which
may be abbreviated) are:
string cat ?string1? ?string2...?
Concatenate the given strings just like placing them directly next to each other │
and return the resulting compound string. If no strings are present, the result is │
an empty string. │
This primitive is occasionally handier than juxtaposition of strings when mixed │
quoting is wanted, or when the aim is to return the result of a concatenation │
without resorting to return -level 0, and is more efficient than building a list of │
arguments and using join with an empty join string. │
string compare ?-nocase? ?-length length? 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 length? 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 index 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 described in STRING INDICES), 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
described in the STRING INDICES section.
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 includes characters
outside of the [0-9] range.
double Any of the forms allowed to Tcl_GetDoubleFromObj.
entier Any of the valid string formats for an integer value of arbitrary size │
in Tcl, with optional surrounding whitespace. The formats accepted are │
exactly those accepted by the C routine Tcl_GetBignumFromObj.
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 overflow in the value, 0
is returned 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, mongolian vowel separator (U+180e),
zero width space (U+200b), word joiner (U+2060) or zero width no-break
space (U+feff) (=BOM).
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 overflow in the value, 0 is
returned and the varname will contain -1.
wordchar Any Unicode word character. That is any alphanumeric character, and
any Unicode connector punctuation 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 return 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 index 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 described in STRING INDICES), 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 number of bytes used to store the string. If
the value is a byte array value (such as those returned from reading a binary
encoded channel), then this will return the actual byte length of the value.
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
-nocase is specified, then matching is done without regard to case differences.
Both key and value may be multiple characters. Replacement 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, including 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 characters *?[]\ 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. The initial string is returned untouched, if first
is greater than last, or if first is equal to or greater than the length of the
initial string, or last is less than 0.
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
using the forms described in STRING INDICES.
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 upper 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 using the forms described in STRING
INDICES.
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
using the forms described in STRING INDICES.
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 removed. If chars is not specified then
white space is removed (any character for which string is space returns 1, and
"\0").
string trimleft string ?chars?
Returns a value equal to string except that any leading characters present in the
string given by chars are removed. If chars is not specified then white space is
removed (any character for which string is space returns 1, and "\0").
string trimright string ?chars?
Returns a value equal to string except that any trailing characters present in the
string given by chars are removed. If chars is not specified then white space is
removed (any character for which string is space returns 1, and "\0").
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 represent string in
memory when encoded as Tcl's internal modified UTF-8; Tcl may use other encodings
for string as well, and does not guarantee to only use a single encoding for a
particular string. Because UTF-8 uses a variable number of 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
determining the length of a Tcl byte array value). Refer to the Tcl_NumUtfChars
manual entry for more details on the UTF-8 representation.
Formally, the string bytelength operation returns the content of the length field
of the Tcl_Obj structure, after calling Tcl_GetString to ensure that the bytes
field is populated. This is highly unlikely to be useful to Tcl scripts, as Tcl's
internal encoding is not strict UTF-8, but rather a modified CESU-8 with a
denormalized NUL (identical to that used in a number of places by Java's
serialization mechanism) to enable basic processing with non-Unicode-aware C
functions. As this representation should only ever be used by Tcl's
implementation, the number of bytes used to store the representation is of very low
value (except to C extension code, which has direct access for the purpose of
memory management, etc.)
Compatibility note: it is likely that this subcommand will be withdrawn in a future
version of Tcl. It is better to use the encoding convertto command to convert a
string to a known encoding and then apply string length to that.
string length [encoding convertto utf-8 $theString]
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 using the forms in
STRING INDICES. 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 using the forms in STRING INDICES. 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 INDICES
When referring to indices into a string (e.g., for string index or string range) the
following formats are supported:
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 integer 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.
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(3tcl), list(3tcl)
KEYWORDS
case conversion, compare, index, match, pattern, string, word, equal, ctype, character,
reverse