strcpy(3) — Linux manual page

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
       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

       #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)

COLOPHON

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Linux man-pages 6.9.1          2024-06-15                      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)

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