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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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()

       The Base Definitions volume of POSIX.1-2017, <string.h>

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(3)
