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--- system-programming:getenv-setenv [2024/04/19 18:02] – ایجاد شد pejman
+++ system-programming:getenv-setenv [2024/06/18 01:23] (فعلی) – حذف شد pejman
@@ خط 1: / خط 1: @@
-====== تابع ()getenv و ()setenv - خواندن و نوشتن متغیر های محلی ======
-----
-==== تابع ()getenv ====
-<code C>
-// man 1 env
-// man 3 getenv
-/* getenv() returns a pointer to the value in the environment, or NULL if there is no match. */
-#include <stdlib.h>
-char *getenv(const char *name);
-</code>
-<code C>
-/* env-var.c */
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-int main(void)
-{
-   /* Using getenv() to fetch env. variables */
-   printf("Your username is %s\n", getenv("USER"));
-   printf("Your home directory is %s\n",
-      getenv("HOME"));
-   printf("Your preferred editor is %s\n",
-      getenv("EDITOR"));
-   printf("Your shell is %s\n", getenv("SHELL"));
-   /* Check if the current terminal support colors*/
-   if ( strstr(getenv("TERM"), "256color")  )
-   {
-      /* Color the output with \033 + colorcode */
-      printf("\033[0;31mYour \033[0;32mterminal "
-         "\033[0;35msupport "
-         "\033[0;33mcolors\033[0m\n");
-   }
-   else
-   {
-      printf("Your terminal doesn't support"
-         " colors\n");
-   }
-   return 0;
-}
-</code>
-  $ make env-var
-  cc     env-var.c   -o env-var
-  $ ./env-var
-  Your username is pejman
-  Your home directory is /home/pejman
-  Your preferred editor is (null)
-  Your shell is /bin/bash
-  Your terminal support colors
-  $ echo $USER
-  pejman
-  $ echo $HOME
-  /home/pejman
-  $ echo $EDITOR
-  $ echo $SHELL
-  /bin/bash
-  $ echo $TERM
-  xterm-256color
-  $ export TERM=xterm
-  $ ./env-var
-  Your username is pejman
-  Your home directory is /home/pejman
-  Your preferred editor is (null)
-  Your shell is /bin/bash
-  Your terminal doesn't support colors
-  $ export TERM=xterm-256color
-  $ echo $TERM
-  xterm-256color
-  $ TERM=xterm ./env-var
-  Your username is pejman
-  Your home directory is /home/pejman
-  Your preferred editor is (null)
-  Your shell is /bin/bash
-  Your terminal doesn't support colors
-  $ echo $TERM
-  xterm-256color
-----
-==== تابع ()setenv ====
-<code C>
-// man 3 setenv
-/* The  setenv()  function adds the variable name to the environment with the value value.
- * if variable exists and overwrite is zero, then the value of name is not changed.
-*/
-#include <stdlib.h>
-int setenv(const char *name, const char *value, int overwrite);
-</code>
-<code C>
-/* env-var-set.c */
-#define _POSIX_C_SOURCE 200112L
-#include <stdio.h>
-#include <stdlib.h>
-int main(void)
-{
-    setenv("FULLNAME", "Jack-Benny", 1);
-    printf("Your full name is %s\n", getenv("FULLNAME"));
-    return 0;
-}
-</code>
-  $ make env-var-set
-  cc     env-var-set.c   -o env-var-set
-  $ ./env-var-set
-  Your full name is Jack-Benny
-  $ echo $FULLNAME