string.3c (2010 09)

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string(3C) string(3C)

the strings that determines their relative ordering usually comes among the ﬁrst few characters.

strxfrm() offers better performance in, for example, a sorting routine where a number of strings are

each transformed just once and the transformed versions are compared against each other many times.

EXTERNAL INFLUENCES

Locale

The

LC_CTYPE category determines the interpretation of the bytes within the string arguments to the

strcoll() and strxfrm() functions as single and/or multibyte characters. It also determines the

case conversions to be done for the strcasecmp()

and strncasecmp() functions.

The

LC_COLLATE category determines the collation ordering used by the

strcoll() and strxfrm()

functions.

International Code Set Support

Single- and multibyte character code sets are supported for the

strcoll() and strxfrm() functions.

Only single-byte character code sets are supported for the

strcasecmp() and strncasecmp() func-

tions.

EXAMPLES

The following sample piece of code ﬁnds the tokens, separated by blanks, that are in the string s (assum-

ing that there are at most

MAXTOK tokens):

inti=0;

char *s, *last, *tok[MAXTOK];

tok[0] = strtok_r(s, " ", &last);

while (tok[++i] = strtok_r(NULL, " ", &last));

WARNINGS

The functions strcat(), strncat(), strcpy(), strncpy(), strtok(), and strtok_r() alter

the contents of the array to which s1 points. They do not check for overﬂow of the array.

Null pointers for destination strings cause undeﬁned behavior.

Character movement is performed differently in different implementations, so moves involving overlap-

ping source and destination strings may yield surprises.

The transformed string produced by

strxfrm() for a language using an 8-bit code set is usually at

least twice as large as the original string and may be as much four times as large (ordinary characters

occupy two bytes each in the transformed string, 1-to-2 characters four bytes, 2-to-1 characters two bytes

per original pair, and don’t-care characters no bytes). Each character of a multibyte code set (Asian

languages) occupies three bytes in the transformed string.

For functions

strcoll() and strxfrm() results are undeﬁned if the languages speciﬁed by the

LC_COLLATE and LC_CTYPE categories use different code sets.

Users of

strtok_r() should also note that the prototype of this function will change in the next release

for conformance with the new POSIX Threads standard.

AUTHOR

string() was developed by the University of California, Berkeley, AT&T, OSF, and HP.