strlen(3p) — Linux manual page

STRLEN(3P)              POSIX Programmer's Manual             STRLEN(3P)

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.

NAME

       strlen, strnlen — get length of fixed size string

SYNOPSIS

       #include <string.h>

       size_t strlen(const char *s);
       size_t strnlen(const char *s, size_t maxlen);

DESCRIPTION

       For strlen(): 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 POSIX.1‐2017 defers to the ISO C
       standard.

       The strlen() function shall compute the number of bytes in the
       string to which s points, not including the terminating NUL
       character.

       The strnlen() function shall compute the smaller of the number of
       bytes in the array to which s points, not including any
       terminating NUL character, or the value of the maxlen argument.
       The strnlen() function shall never examine more than maxlen bytes
       of the array pointed to by s.

RETURN VALUE

       The strlen() function shall return the length of s; no return
       value shall be reserved to indicate an error.

       The strnlen() function shall return the number of bytes preceding
       the first null byte in the array to which s points, if s contains
       a null byte within the first maxlen bytes; otherwise, it shall
       return maxlen.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

   Getting String Lengths
       The following example sets the maximum length of key and data by
       using strlen() to get the lengths of those strings.

           #include <string.h>
           ...
           struct element {
               char *key;
               char *data;
           };
           ...
           char *key, *data;
           int len;

           *keylength = *datalength = 0;
           ...
           if ((len = strlen(key)) > *keylength)
               *keylength = len;
           if ((len = strlen(data)) > *datalength)
               *datalength = len;
           ...

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       wcslen(3p)

       The Base Definitions volume of POSIX.1‐2017, string.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                        STRLEN(3P)

Pages that refer to this page: string.h(0p), localeconv(3p), strnlen(3p), wcslen(3p)

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