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()

       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 .