@(#)getenv.3 6.3 (Berkeley) 03/11/87

.AT 3 getenv, setenv, unsetenv - manipulate environmental variables

 char *getenv(name)  char *name; 

 setenv(name, value, overwrite)  char *name, value;  int overwrite; 

 void unsetenv(name)  char *name; 

Getenv searches the environment list (see environ(7)) for a string of the form name=value and returns a pointer to the string value if such a string is present, and 0 (NULL) if it is not.

Setenv searches the environment list as getenv does; if the string name is not found, a string of the form name=value is added to the environment. If it is found and overwrite is non-zero, its value is changed to value. Setenv returns 0 on success and -1 on failure.

Unsetenv removes all occurrences of the string name from the environment.

All of these routines permit, but do not require, a trailing equals (``='') sign on name or a leading equals sign on value.

csh(1), sh(1), execve(2), environ(7)