'\" t
.\" Copyright 2005-2013, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strtok_r 3 2026-02-25 "Linux man-pages 6.19"
.SH NAME
strtok_r \- string tokenize reentrant
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BI "char *strtok_r(char *_Nullable restrict " str \
", const char *restrict " delim ,
.BI "               char **restrict " saveptr );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR strtok_r ():
.nf
    _POSIX_C_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
The
.BR strtok_r ()
function is a reentrant version of
.BR strtok (3).
.P
The
.I saveptr
argument is a pointer to a
.I char\~*
variable that is used internally by
.BR strtok_r ()
in order to maintain context between successive calls that parse the
same string.
.P
On the first call to
.BR strtok_r (),
.I str
should point to the string to be parsed, and the value of
.I *saveptr
is ignored (but see VERSIONS).
In subsequent calls,
.I str
should be NULL, and
.I saveptr
(and the buffer that it points to)
should be unchanged since the previous call.
.P
Different strings may be parsed concurrently using sequences of calls to
.BR strtok_r ()
that specify different
.I saveptr
arguments.
.SH RETURN VALUE
.BR strtok_r ()
returns a pointer to the next token,
or NULL if there are no more tokens.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR strtok_r ()
T}	Thread safety	MT-Safe
.TE
.SH VERSIONS
On some implementations,
.\" Tru64, according to its manual page
.I *saveptr
is required to be NULL on the first call to
.BR strtok_r ()
that is being used to parse
.IR str .
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001.
.SH EXAMPLES
The program below uses nested loops that employ
.BR strtok_r ()
to break a string into a two-level hierarchy of tokens.
The first command-line argument specifies the string to be parsed.
The second argument specifies the delimiter byte(s)
to be used to separate that string into "major" tokens.
The third argument specifies the delimiter byte(s)
to be used to separate the "major" tokens into subtokens.
.P
An example of the output produced by this program is the following:
.P
.in +4n
.EX
.RB "$" " ./a.out \[aq]a/bbb///cc;xxx:yyy:\[aq] \[aq]:;\[aq] \[aq]/\[aq]"
1: a/bbb///cc
         \-\-> a
         \-\-> bbb
         \-\-> cc
2: xxx
         \-\-> xxx
3: yyy
         \-\-> yyy
.EE
.in
.SS Program source
\&
.\" SRC BEGIN (strtok.c)
.EX
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
\&
int
main(int argc, char *argv[])
{
    char *str1, *str2, *token, *subtoken;
    char *saveptr1, *saveptr2;
    int j;
\&
    if (argc != 4) {
        fprintf(stderr, "Usage: %s string delim subdelim\[rs]n",
                argv[0]);
        exit(EXIT_FAILURE);
    }
\&
    for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {
        token = strtok_r(str1, argv[2], &saveptr1);
        if (token == NULL)
            break;
        printf("%d: %s\[rs]n", j, token);
\&
        for (str2 = token; ; str2 = NULL) {
            subtoken = strtok_r(str2, argv[3], &saveptr2);
            if (subtoken == NULL)
                break;
            printf("\[rs]t \-\-> %s\[rs]n", subtoken);
        }
    }
\&
    exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR strtok (3)