strcpy(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | STANDARDS | CAVEATS | EXAMPLES | SEE ALSO

strcpy(3)               Library Functions Manual               strcpy(3)

NAME         top

       stpcpy, strcpy, strcat - copy or catenate a string

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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 destination 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         top

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

       strcpy()
       strcat()
              These functions return dst.

ATTRIBUTES         top

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

STANDARDS         top

       stpcpy()
              POSIX.1-2008.

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

STANDARDS         top

       stpcpy()
              POSIX.1-2008.

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

CAVEATS         top

       The strings src and dst may not overlap.

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

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

EXAMPLES         top

       #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         top

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

Linux man-pages (unreleased)   2024-05-02                      strcpy(3)

Pages that refer to this page: bcopy(3)memccpy(3)memcpy(3)memmove(3)string(3)wcpcpy(3)wcscat(3)wcscpy(3)feature_test_macros(7)signal-safety(7)string_copying(7)