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1.1 ! root 1: .\" @(#)getenv.3 6.4 (Berkeley) 3/20/87 ! 2: .\" ! 3: .TH GETENV 3 "March 20, 1987" ! 4: .AT 3 ! 5: .SH NAME ! 6: getenv, setenv, unsetenv \- manipulate environmental variables ! 7: .SH SYNOPSIS ! 8: .nf ! 9: .B char *getenv(name) ! 10: .B char *name; ! 11: .PP ! 12: .B setenv(name, value, overwrite) ! 13: .B char *name, value; ! 14: .B int overwrite; ! 15: .PP ! 16: .B void unsetenv(name) ! 17: .B char *name; ! 18: .fi ! 19: .SH DESCRIPTION ! 20: \fIGetenv\fP searches the environment list (see \fIenviron\fP(7)) ! 21: for a string of the form \fIname\fP\fB=\fP\fIvalue\fP and returns ! 22: a pointer to the string \fIvalue\fP if such a string is present, ! 23: and 0 (NULL) if it is not. ! 24: .PP ! 25: \fISetenv\fP searches the environment list as \fIgetenv\fP does; if ! 26: the string \fIname\fP is not found, a string of the form ! 27: \fIname\fP\fB=\fP\fIvalue\fP is added to the environment. If it is ! 28: found, and \fIoverwrite\fP is non-zero, its value is changed to ! 29: \fIvalue\fP. \fISetenv\fP returns 0 on success and -1 on failure, ! 30: where failure is caused by an inability to allocate space for the ! 31: environment. ! 32: .PP ! 33: \fIUnsetenv\fP removes all occurrences of the string \fIname\fP from ! 34: the environment. There is no library provision for completely removing ! 35: the current environment. It is suggested that the following code be ! 36: used to do so. ! 37: .PP ! 38: .nf ! 39: static char *envinit[1]; ! 40: extern char **environ; ! 41: environ = envinit; ! 42: .fi ! 43: .PP ! 44: All of these routines permit, but do not require, a trailing equals ! 45: (``='') sign on \fIname\fP or a leading equals sign on \fIvalue\fP. ! 46: .SH SEE ALSO ! 47: csh(1), sh(1), execve(2), environ(7)
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