users_groups/t_getpwnam_r.c

This is users_groups/t_getpwnam_r.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is a supplementary file for Chapter 8.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

Download users_groups/t_getpwnam_r.c

Cover of The Linux Programming Interface

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Function list (Bold in this list means a function is not static)

main()

/* t_getpwnam_r.c

   Demonstrate the use of getpwnam_r() to retrieve the password record for
   a named user from the system password file.
*/
#include <pwd.h>
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s username\n", argv[0]);

    size_t bufSize = sysconf(_SC_GETPW_R_SIZE_MAX);
    char *buf = malloc(bufSize);
    if (buf == NULL)
        errExit("malloc %zu", bufSize);

    struct passwd *result;
    struct passwd pwd;

    int s = getpwnam_r(argv[1], &pwd, buf, bufSize, &result);
    if (s != 0)
        errExitEN(s, "getpwnam_r");

    if (result != NULL)
        printf("Name: %s\n", pwd.pw_gecos);
    else
        printf("Not found\n");

    exit(EXIT_SUCCESS);
}

Download users_groups/t_getpwnam_r.c

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