unsetenv - remove an environment variable
The unsetenv() function shall remove an environment variable from the environment of the calling process. The name argument points to a string, which is the name of the variable to be removed. The named argument shall not contain an '=' character. If the named variable does not exist in the current environment, the environment shall be unchanged and the function is considered to have completed successfully.
The unsetenv() function shall update the list of pointers to which environ points.
The unsetenv() function need not be thread-safe.
Upon successful completion, zero shall be returned. Otherwise, -1 shall be returned, errno set to indicate the error, and the environment shall be unchanged.
The unsetenv() function shall fail if:
- The name argument points to an empty string, or points to a string containing an '=' character.
Refer to the RATIONALE section in setenv.
XBD <stdlib.h>, <sys/types.h>
First released in Issue 6. Derived from the IEEE P1003.1a draft standard.
Austin Group Interpretation 1003.1-2001 #156 is applied.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0698  and XSH/TC1-2008/0699  are applied.
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