'\" t .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .\" References consulted: .\" Linux libc source code .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) .\" 386BSD man pages .\" Modified Sat Jul 24 17:57:50 1993 by Rik Faith (faith@cs.unc.edu) .TH strspn 3 2024-05-02 "Linux man-pages 6.8" .SH NAME strspn, strcspn \- get length of a prefix substring .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .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)