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  at-
       tributes(7).

       ┌────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                   │ Attribute     │ Value   │
       ├────────────────────────────────────────────┼───────────────┼─────────┤
       │stpcpy(), strcpy(), strcat()                │ Thread safety │ MT-Safe │
       └────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS
       stpcpy()
              POSIX.1-2008.

       strcpy()
       strcat()
              POSIX.1-2001, POSIX.1-2008, C99, 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  Shlemiel  the painter
       ⟨https://www.joelonsoftware.com/2001/12/11/back-to-basics/⟩.

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 6.03              2023-02-05                         strcpy(3)

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