strncpy(3p) — Linux manual page


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

PROLOG         top

       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         top

       stpncpy, strncpy — copy fixed length string, returning a pointer
       to the array end

SYNOPSIS         top

       #include <string.h>

       char *stpncpy(char *restrict s1, const char *restrict s2, size_t n);
       char *strncpy(char *restrict s1, const char *restrict s2, size_t n);

DESCRIPTION         top

       For strncpy(): 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

       The stpncpy() and strncpy() functions shall copy not more than n
       bytes (bytes that follow a NUL character are not copied) from the
       array pointed to by s2 to the array pointed to by s1.

       If the array pointed to by s2 is a string that is shorter than n
       bytes, NUL characters shall be appended to the copy in the array
       pointed to by s1, until n bytes in all are written.

       If copying takes place between objects that overlap, the behavior
       is undefined.

RETURN VALUE         top

       If a NUL character is written to the destination, the stpncpy()
       function shall return the address of the first such NUL
       character.  Otherwise, it shall return &s1[n].

       The strncpy() function shall return s1.

       No return values are reserved to indicate an error.

ERRORS         top

       No errors are defined.

       The following sections are informative.

EXAMPLES         top



       Applications must provide the space in s1 for the n bytes to be
       transferred, as well as ensure that the s2 and s1 arrays do not

       Character movement is performed differently in different
       implementations. Thus, overlapping moves may yield surprises.

       If there is no NUL character byte in the first n bytes of the
       array pointed to by s2, the result is not null-terminated.

RATIONALE         top




SEE ALSO         top

       strcpy(3p), wcsncpy(3p)

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

COPYRIGHT         top

       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 .

       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 .

IEEE/The Open Group               2017                       STRNCPY(3P)

Pages that refer to this page: string.h(0p)stpncpy(3p)strcpy(3p)wcsncpy(3p)