getenv() — Get value of environment variables
Standards
| Standards / Extensions | C or C++ | Dependencies |
|---|---|---|
ISO C
POSIX.1 XPG4 XPG4.2 C99 Single UNIX Specification, Version 3 |
both |
Format
#include <stdlib.h>
char *getenv(const char *varname);General description
Searches the table of environment variables for an entry corresponding to varname and returns a pointer to a buffer containing the current string value of varname.
Special
behavior for POSIX: Under POSIX, the value of the char
**environ pointer is honored and used by getenv(). You can
declare and use this pointer. Under POSIX(OFF) this is not the case:
the table start cannot be modified.
Usage Note
To avoid changing the environment variables or management process, the caller must ensure not to modify or release the buffer that is pointed by the returned pointer.
Returned value
If successful, getenv() returns a pointer to a buffer containing the current string value of varname. You should copy the string that is returned because a subsequent call to getenv() will overwrite it.
If the varname is not found, getenv() returns a NULL pointer. The returned value is NULL if the given variable is not currently defined.
Example
/* CELEBG05
In this example, *pathvar points to the value of the PATH
environment variable.
In a POSIX environment, this variable would be from the CENV
group ID.
*/
#include <stdlib.h>
#include <stdio.h>
int main(void)
{
char *pathvar;
pathvar = getenv("PATH");
printf("pathvar=%s",pathvar);
}