putenv in c

What is putenv() in c?

putenv in c is a c standard function used to change the environmental variable value.

It is defined in stdlib.h header file.

Prototype

int putenv(char *strng);

Return value

It returns 0 on success -1 on error.

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putenv in c program example

// C program to illustrate putenv function
#include<stdio.h>
#include<stdlib.h>
int main()
{
  int res=putenv("NAME=TST");
  if(res==0)
   printf("Value of environment variable written is :%s \n",getenv("NAME"));
  else
   printf("Error on writing variable\n");
 return 0;
}

Output

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Code explanation

The putenv() changes the environment variable value.

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