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 bytelength string
- Returns a decimal string giving the number of bytes used to
represent 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 determining the length of a Tcl ByteArray
object). Refer to the Tcl_NumUtfChars manual entry for more details
on the UTF-8 representation.
- 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 string1 string2
?startIndex?
- Search string2 for a sequence of characters that
exactly match the characters in string1. If found, return the index
of the first character in the first such match within string2. 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 string2 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
- The char specified at this integral index.
- end
- The last char of the string.
- end-integer
- The last char of the string minus the specified integer
offset (e.g. end-1 would refer to the "c" in
"abcd").
If
charIndex is less than 0 or greater than or equal to the length of the
string then an empty string is returned.
- 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 and 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 the function 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 valid forms for a double in Tcl, with optional
surrounding whitespace. In case of under/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 forms for an ordinary integer in Tcl, with
optional surrounding whitespace. In case of under/overflow in the value, 0
is returned and the varname will contain -1.
- lower
- Any Unicode lower case alphabet character.
- print
- Any Unicode printing character, including space.
- punct
- Any Unicode punctuation character.
- space
- Any Unicode space character.
- 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.
- 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 string1 string2
?lastIndex?
- Search string2 for a sequence of characters that
exactly match the characters in string1. If found, return the index
of the first character in the last such match within string2. If
there is no match, then return -1. If lastIndex is specified (in
any of the forms accepted by the index method), then only the
characters in string2 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 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
-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 doesn't. 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 ('_' 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. 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 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 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 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 from the set given by chars are
removed. 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 characters from the set given by chars are removed. If
chars is not specified then white space is removed (spaces, tabs,
newlines, and carriage returns).
- string trimright string ?chars?
- Returns a value equal to string except that any
trailing characters from the set given by chars are removed. If
chars is not specified then white space is removed (spaces, tabs,
newlines, and carriage returns).
- 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 underscore (Unicode connector punctuation) characters, or any
single 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(3tcl), list(3tcl)
KEYWORDS¶
case conversion, compare, index, match, pattern, string, word, equal,
ctype