setenv(3) Library Functions Manual setenv(3) setenv - (libc -lc) #include int setenv(const char *name, const char *value, int overwrite); int unsetenv(const char *name); glibc ( feature_test_macros(7)): setenv() unsetenv(): _POSIX_C_SOURCE >= 200112L || /* glibc <= 2.19: */ _BSD_SOURCE setenv() name value name . name value overwrite overwrite name ( setenv() ). name value ( putenv(3)). unsetenv() name . name . setenv() unsetenv() -1 errno . EINVAL name NULL 0 '='. ENOMEM . attributes(7). +-----------+------------------------------------+---------------------+ || | | +-----------+------------------------------------+---------------------+ |setenv(), | | MT-Unsafe const:env | |unsetenv() | | | +-----------+------------------------------------+---------------------+ POSIX.1-2008. POSIX.1-2001 4.3BSD. glibc 2.2.2 unsetenv() void glibc POSIX.1 . POSIX.1 setenv() unsetenv() . POSIX.1 name '=' setenv() EINVAL glibc glibc 2.3.4 '=' name. clearenv(3) getenv(3) putenv(3) environ(7) 3 . . : . 6.18 8 2026 setenv(3)