PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

STRTOK(3P)                POSIX Programmer's Manual               STRTOK(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       strtok, strtok_r — split string into tokens

SYNOPSIS         top

       #include <string.h>

       char *strtok(char *restrict s1, const char *restrict s2);
       char *strtok_r(char *restrict s, const char *restrict sep,
           char **restrict lasts);

DESCRIPTION         top

       For strtok(): The functionality described on this reference page is
       aligned with the ISO C standard. Any conflict between the
       requirements described here and the ISO C standard is unintentional.
       This volume of POSIX.1‐2008 defers to the ISO C standard.

       A sequence of calls to strtok() breaks the string pointed to by s1
       into a sequence of tokens, each of which is delimited by a byte from
       the string pointed to by s2.  The first call in the sequence has s1
       as its first argument, and is followed by calls with a null pointer
       as their first argument. The separator string pointed to by s2 may be
       different from call to call.

       The first call in the sequence searches the string pointed to by s1
       for the first byte that is not contained in the current separator
       string pointed to by s2.  If no such byte is found, then there are no
       tokens in the string pointed to by s1 and strtok() shall return a
       null pointer. If such a byte is found, it is the start of the first
       token.

       The strtok() function then searches from there for a byte that is
       contained in the current separator string. If no such byte is found,
       the current token extends to the end of the string pointed to by s1,
       and subsequent searches for a token shall return a null pointer. If
       such a byte is found, it is overwritten by a NUL character, which
       terminates the current token. The strtok() function saves a pointer
       to the following byte, from which the next search for a token shall
       start.

       Each subsequent call, with a null pointer as the value of the first
       argument, starts searching from the saved pointer and behaves as
       described above.

       The implementation shall behave as if no function defined in this
       volume of POSIX.1‐2008 calls strtok().

       The strtok() function need not be thread-safe.

       The strtok_r() function considers the null-terminated string s as a
       sequence of zero or more text tokens separated by spans of one or
       more characters from the separator string sep.  The argument lasts
       points to a user-provided pointer which points to stored information
       necessary for strtok_r() to continue scanning the same string.

       In the first call to strtok_r(), s points to a null-terminated
       string, sep to a null-terminated string of separator characters, and
       the value pointed to by lasts is ignored. The strtok_r() function
       shall return a pointer to the first character of the first token,
       write a null character into s immediately following the returned
       token, and update the pointer to which lasts points.

       In subsequent calls, s is a null pointer and lasts shall be unchanged
       from the previous call so that subsequent calls shall move through
       the string s, returning successive tokens until no tokens remain. The
       separator string sep may be different from call to call. When no
       token remains in s, a null pointer shall be returned.

RETURN VALUE         top

       Upon successful completion, strtok() shall return a pointer to the
       first byte of a token. Otherwise, if there is no token, strtok()
       shall return a null pointer.

       The strtok_r() function shall return a pointer to the token found, or
       a null pointer when no token is found.

ERRORS         top

       No errors are defined.

       The following sections are informative.

EXAMPLES         top

   Searching for Word Separators
       The following example searches for tokens separated by <space>
       characters.

           #include <string.h>
           ...
           char *token;
           char line[] = "LINE TO BE SEPARATED";
           char *search = " ";

           /* Token will point to "LINE". */
           token = strtok(line, search);

           /* Token will point to "TO". */
           token = strtok(NULL, search);

   Find First two Fields in a Buffer
       The following example uses strtok() to find two character strings (a
       key and data associated with that key) separated by any combination
       of <space>, <tab>, or <newline> characters at the start of the array
       of characters pointed to by buffer.

           #include <string.h>
           ...
           char    *buffer;
           ...
           struct element {
               char *key;
               char *data;
           } e;
           ...
           // Load the buffer...
           ...
           // Get the key and its data...
           e.key = strtok(buffer, " \t\n");
           e.data = strtok(NULL, " \t\n");
           // Process the rest of the contents of the buffer...
           ...

APPLICATION USAGE         top

       The strtok_r() function is thread-safe and stores its state in a
       user-supplied buffer instead of possibly using a static data area
       that may be overwritten by an unrelated call from another thread.

RATIONALE         top

       The strtok() function searches for a separator string within a larger
       string. It returns a pointer to the last substring between separator
       strings.  This function uses static storage to keep track of the
       current string position between calls. The new function, strtok_r(),
       takes an additional argument, lasts, to keep track of the current
       position in the string.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       The Base Definitions volume of POSIX.1‐2008, string.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) In the event of any discrepancy between this version and
       the original IEEE and The Open Group Standard, the original IEEE and
       The Open Group Standard is the referee document. The original
       Standard can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                          STRTOK(3P)

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