1.\" Copyright (c) 1988, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)getenv.3 8.2 (Berkeley) 12/11/93 37.\" $FreeBSD$ 38.\" 39.Dd December 11, 1993 40.Dt GETENV 3 41.Os 42.Sh NAME 43.Nm getenv , 44.Nm putenv , 45.Nm setenv , 46.Nm unsetenv 47.Nd environment variable functions 48.Sh SYNOPSIS 49.Fd #include <stdlib.h> 50.Ft char * 51.Fn getenv "const char *name" 52.Ft int 53.Fn setenv "const char *name" "const char *value" "int overwrite" 54.Ft int 55.Fn putenv "const char *string" 56.Ft void 57.Fn unsetenv "const char *name" 58.Sh DESCRIPTION 59These functions set, unset and fetch environment variables from the 60host 61.Em environment list . 62For compatibility with differing environment conventions, 63the given arguments 64.Ar name 65and 66.Ar value 67may be appended and prepended, 68respectively, 69with an equal sign 70.Dq Li \&= . 71.Pp 72The 73.Fn getenv 74function obtains the current value of the environment variable, 75.Ar name . 76If the variable 77.Ar name 78is not in the current environment, 79a null pointer is returned. 80.Pp 81The 82.Fn setenv 83function inserts or resets the environment variable 84.Ar name 85in the current environment list. 86If the variable 87.Ar name 88does not exist in the list, 89it is inserted with the given 90.Ar value. 91If the variable does exist, the argument 92.Ar overwrite 93is tested; if 94.Ar overwrite is 95zero, the 96variable is not reset, otherwise it is reset 97to the given 98.Ar value . 99.Pp 100The 101.Fn putenv 102function takes an argument of the form ``name=value'' and is 103equivalent to: 104.Bd -literal -offset indent 105setenv(name, value, 1); 106.Ed 107.Pp 108The 109.Fn unsetenv 110function 111deletes all instances of the variable name pointed to by 112.Fa name 113from the list. 114.Sh RETURN VALUES 115The functions 116.Fn setenv 117and 118.Fn putenv 119return zero if successful; otherwise the global variable 120.Va errno 121is set to indicate the error and a 122\-1 is returned. 123.Sh ERRORS 124.Bl -tag -width [ENOMEM] 125.It Bq Er ENOMEM 126The function 127.Fn setenv 128or 129.Fn putenv 130failed because they were unable to allocate memory for the environment. 131.El 132.Sh SEE ALSO 133.Xr csh 1 , 134.Xr sh 1 , 135.Xr execve 2 , 136.Xr environ 7 137.Sh STANDARDS 138The 139.Fn getenv 140function conforms to 141.St -ansiC . 142.Sh HISTORY 143The functions 144.Fn setenv 145and 146.Fn unsetenv 147appeared in 148.At v7 . 149The 150.Fn putenv 151function appeared in 152.Bx 4.3 Reno . 153