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 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
       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 attributes(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 6.9.1              2024-06-15                         strcpy(3)

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