strcpy(3) - Man pages

strcpy(3)                  Library Functions Manual                  strcpy(3)

NAME
       stpcpy, strcpy, strcat - copy or catenate a string

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <string.h>

       char *stpcpy(char *restrict dst, const char *restrict src);
       char *strcpy(char *restrict dst, const char *restrict src);
       char *strcat(char *restrict dst, const char *restrict src);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       stpcpy():
           Since glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _GNU_SOURCE

DESCRIPTION
       stpcpy()
       strcpy()
              These functions copy the string pointed to by src, into a string
              at  the buffer pointed to by dst.  The programmer is responsible
              for allocating a  destination  buffer  large  enough,  that  is,
              strlen(src)  + 1.  For the difference between the two functions,
              see RETURN VALUE.

       strcat()
              This function catenates the string pointed to by src, after  the
              string  pointed  to  by  dst  (overwriting  its terminating null
              byte).  The programmer is responsible for allocating a  destina-
              tion  buffer  large enough, that is, strlen(dst) + strlen(src) +
              1.

       An implementation of these functions might be:

           char *
           stpcpy(char *restrict dst, const char *restrict src)
           {
               char  *p;

               p = mempcpy(dst, src, strlen(src));
               *p = '\0';

               return p;
           }

           char *
           strcpy(char *restrict dst, const char *restrict src)
           {
               stpcpy(dst, src);
               return dst;
           }

           char *
           strcat(char *restrict dst, const char *restrict src)
           {
               stpcpy(dst + strlen(dst), src);
               return dst;
           }

RETURN VALUE
       stpcpy()
              This function returns a pointer to the terminating null byte  of
              the copied string.

       strcpy()
       strcat()
              These functions return dst.

ATTRIBUTES
       For  an  explanation  of  the  terms  used in this section, see attrib-
       utes(7).
       ┌───────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                 │ Attribute     │ Value   │
       ├───────────────────────────────────────────┼───────────────┼─────────┤
       │ stpcpy(), strcpy(), strcat()              │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       stpcpy()
              POSIX.1-2008.

       strcpy()
       strcat()
              C11, POSIX.1-2008.

STANDARDS
       stpcpy()
              POSIX.1-2008.

       strcpy()
       strcat()
              POSIX.1-2001, C89, SVr4, 4.3BSD.

CAVEATS
       The strings src and dst may not overlap.

       If the destination buffer is not large enough, the  behavior  is  unde-
       fined.  See _FORTIFY_SOURCE in feature_test_macros(7).

       strcat() can be very inefficient.  Read about ]8;;https://www.joelonsoftware.com/2001/12/11/back-to-basics/\Shlemiel the painter]8;;\.

EXAMPLES
       #include <err.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>

       int
       main(void)
       {
           char    *p;
           char    *buf1;
           char    *buf2;
           size_t  len, maxsize;

           maxsize = strlen("Hello ") + strlen("world") + strlen("!") + 1;
           buf1 = malloc(sizeof(*buf1) * maxsize);
           if (buf1 == NULL)
               err(EXIT_FAILURE, "malloc()");
           buf2 = malloc(sizeof(*buf2) * maxsize);
           if (buf2 == NULL)
               err(EXIT_FAILURE, "malloc()");

           p = buf1;
           p = stpcpy(p, "Hello ");
           p = stpcpy(p, "world");
           p = stpcpy(p, "!");
           len = p - buf1;

           printf("[len = %zu]: ", len);
           puts(buf1);  // "Hello world!"
           free(buf1);

           strcpy(buf2, "Hello ");
           strcat(buf2, "world");
           strcat(buf2, "!");
           len = strlen(buf2);

           printf("[len = %zu]: ", len);
           puts(buf2);  // "Hello world!"
           free(buf2);

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       strdup(3), string(3), wcscpy(3), string_copying(7)

Linux man-pages 6.7               2023-10-31                         strcpy(3)

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