proc/t_getenv.c

This is proc/t_getenv.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 6.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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.

 

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  Cover of The Linux Programming Interface

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

/* t_getenv.c

   Demonstrate the use of getenv() to retrieve the value of an
   environment variable.
*/
#include "tlpi_hdr.h"
int
main(int argc, char *argv[])
{
    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s environ-var\n", argv[0]);

    char *val = getenv(argv[1]);
    printf("%s\n", (val != NULL) ? val : "No such variable");

    exit(EXIT_SUCCESS);
}

 

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