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GETENV (3) | C library functions | Unix Manual Pages | :man

NAME

getenv, putenv, setenv, unsetenv - environment variable functions

CONTENTS

Library
Synopsis
Description
Return Values
Errors
See Also
Standards
History
Bugs

LIBRARY


.Lb libc

SYNOPSIS


.In stdlib.h char * getenv "const char *name" int setenv "const char *name" "const char *value" "int overwrite" int putenv "const char *string" void unsetenv "const char *name"

DESCRIPTION

These functions set, unset and fetch environment variables from the host environment list. For compatibility with differing environment conventions, the given arguments name and value may be appended and prepended, respectively, with an equal sign "=".

The getenv function obtains the current value of the environment variable, name.

The setenv function inserts or resets the environment variable name in the current environment list. If the variable name does not exist in the list, it is inserted with the given value. If the variable does exist, the argument overwrite is tested; if overwrite is zero, the variable is not reset, otherwise it is reset to the given value.

The putenv function takes an argument of the form ‘‘name=value’’ and is equivalent to:
setenv(name, value, 1);

The unsetenv function deletes all instances of the variable name pointed to by name from the list.

RETURN VALUES

The getenv function returns the value of the environment variable as a NUL -terminated string. If the variable name is not in the current environment, NULL is returned.


.Rv -std setenv putenv

ERRORS

[ENOMEM]
The function setenv or putenv failed because they were unable to allocate memory for the environment.

SEE ALSO

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

STANDARDS

HISTORY

BUGS


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