'\" t
.\" Copyright, The contributors to the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strspn 3 2025-05-06 "Linux man-pages 6.14"
.SH NAME
strspn, strcspn \- get length of a prefix substring
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BI "size_t strspn(const char *" s ", const char *" accept );
.BI "size_t strcspn(const char *" s ", const char *" reject );
.fi
.SH DESCRIPTION
The
.BR strspn ()
function calculates the length (in bytes) of the initial
segment of
.I s
which consists entirely of bytes in
.IR accept .
.P
The
.BR strcspn ()
function calculates the length of the initial
segment of
.I s
which consists entirely of bytes not in
.IR reject .
.SH RETURN VALUE
The
.BR strspn ()
function returns the number of bytes in
the initial segment of
.I s
which consist only of bytes
from
.IR accept .
.P
The
.BR strcspn ()
function returns the number of bytes in
the initial segment of
.I s
which are not in the string
.IR reject .
.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 strspn (),
.BR strcspn ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C89, SVr4, 4.3BSD.
.SH SEE ALSO
.BR memchr (3),
.BR strchr (3),
.BR string (3),
.BR strpbrk (3),
.BR strsep (3),
.BR strstr (3),
.BR strtok (3),
.BR wcscspn (3),
.BR wcsspn (3)