.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\"     @(#)strspn.3	8.1 (Berkeley) 6/4/93
.\"
.Dd May 24, 2014
.Dt STRSPN 3
.Os
.Sh NAME
.Nm strspn ,
.Nm strcspn
.Nd span a string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft size_t
.Fn strspn "const char *s" "const char *charset"
.Ft size_t
.Fn strcspn "const char *s" "const char *charset"
.Sh DESCRIPTION
The
.Fn strspn
function
spans the initial part of the null-terminated string
.Fa s
as long as the characters from
.Fa s
occur in the null-terminated string
.Fa charset .
In other words, it computes the string array index
of the first character of
.Fa s
which is not in
.Fa charset ,
else the index of the first null character.
.Pp
The
.Fn strcspn
function
spans the initial part of the null-terminated string
.Fa s
as long as the characters from
.Fa s
.Sy do not
occur in the null-terminated string
.Fa charset
.Po it spans the
.Sy complement
of
.Fa charset
.Pc .
In other words, it computes the string array index
of the first character of
.Fa s
which is also in
.Fa charset ,
else the index of the first null character.
.Sh RETURN VALUES
The
.Fn strspn
and
.Fn strcspn
functions
return the number of characters spanned.
.Sh SEE ALSO
.Xr memchr 3 ,
.Xr strchr 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strstr 3 ,
.Xr strtok 3 ,
.Xr wcsspn 3
.Sh STANDARDS
The
.Fn strspn
and
.Fn strcspn
functions
conform to
.St -isoC .