.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "STRTOK" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" strtok 
.SH PROLOG
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.
.SH NAME
strtok, strtok_r \- split string into tokens
.SH SYNOPSIS
.LP
\fB#include <string.h>
.br
.sp
char *strtok(char *restrict\fP \fIs1\fP\fB, const char *restrict\fP
\fIs2\fP\fB);
.br
\fP
.LP
\fBchar *strtok_r(char *restrict\fP \fIs\fP\fB, const char *restrict\fP
\fIsep\fP\fB,
.br
\ \ \ \ \ \  char **restrict\fP \fIlasts\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
For \fIstrtok\fP():   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
IEEE\ Std\ 1003.1-2001 defers to the ISO\ C standard. 
.LP
A sequence of calls to \fIstrtok\fP() breaks the string pointed to
by \fIs1\fP into a sequence of tokens, each of which is
delimited by a byte from the string pointed to by \fIs2\fP. The first
call in the sequence has \fIs1\fP as its first argument,
and is followed by calls with a null pointer as their first argument.
The separator string pointed to by \fIs2\fP may be different
from call to call.
.LP
The first call in the sequence searches the string pointed to by \fIs1\fP
for the first byte that is \fInot\fP contained in
the current separator string pointed to by \fIs2\fP. If no such byte
is found, then there are no tokens in the string pointed to
by \fIs1\fP and \fIstrtok\fP() shall return a null pointer. If such
a byte is found, it is the start of the first token.
.LP
The \fIstrtok\fP() function then searches from there for a byte that
\fIis\fP 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 \fIs1\fP, and subsequent searches for a token
shall return a null pointer. If such a byte is found, it is overwritten
by a null byte, which terminates the current token. The
\fIstrtok\fP() function saves a pointer to the following byte, from
which the next search for a token shall start.
.LP
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.
.LP
The implementation shall behave as if no function defined in this
volume of IEEE\ Std\ 1003.1-2001 calls
\fIstrtok\fP().
.LP
The
\fIstrtok\fP() function need not be reentrant. A function that is
not required to be reentrant is not required to be thread-safe.
.LP
The \fIstrtok_r\fP() function considers the null-terminated string
\fIs\fP as a sequence of zero or more text tokens separated by
spans of one or more characters from the separator string \fIsep\fP.
The argument \fIlasts\fP points to a user-provided pointer
which points to stored information necessary for \fIstrtok_r\fP()
to continue scanning the same string.
.LP
In the first call to \fIstrtok_r\fP(), \fIs\fP points to a null-terminated
string, \fIsep\fP to a null-terminated string of
separator characters, and the value pointed to by \fIlasts\fP is ignored.
The \fIstrtok_r\fP() function shall return a pointer to
the first character of the first token, write a null character into
\fIs\fP immediately following the returned token, and update
the pointer to which \fIlasts\fP points.
.LP
In subsequent calls, \fIs\fP is a NULL pointer and \fIlasts\fP shall
be unchanged from the previous call so that subsequent
calls shall move through the string \fIs\fP, returning successive
tokens until no tokens remain. The separator string \fIsep\fP
may be different from call to call. When no token remains in \fIs\fP,
a NULL pointer shall be returned. 
.SH RETURN VALUE
.LP
Upon successful completion, \fIstrtok\fP() shall return a pointer
to the first byte of a token. Otherwise, if there is no
token, \fIstrtok\fP() shall return a null pointer.
.LP
The \fIstrtok_r\fP() function shall return a pointer to the token
found, or a NULL pointer when no token is found. 
.SH ERRORS
.LP
No errors are defined.
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Searching for Word Separators
.LP
The following example searches for tokens separated by <space>s.
.sp
.RS
.nf

\fB#include <string.h>
\&...
char *token;
char *line = "LINE TO BE SEPARATED";
char *search = " ";
.sp

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

/* Token will point to "TO". */
token = strtok(NULL, search);
\fP
.fi
.RE
.SS Breaking a Line
.LP
The following example uses \fIstrtok\fP() to break a line into two
character strings separated by any combination of
<space>s, <tab>s, or <newline>s.
.sp
.RS
.nf

\fB#include <string.h>
\&...
struct element {
    char *key;
    char *data;
};
\&...
char line[LINE_MAX];
char *key, *data;
\&...
key = strtok(line, "    \\n");
data = strtok(NULL, "   \\n");
\&...
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
The \fIstrtok_r\fP() 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.
.SH RATIONALE
.LP
The \fIstrtok\fP() 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, \fIstrtok_r\fP(), takes an additional argument, \fIlasts\fP,
to keep track of the current position in the string.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
The Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<string.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .