| .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
| .\" and Copyright (C) 2004, 2007 Michael Kerrisk <mtk.manpages@gmail.com> |
| .\" |
| .\" %%%LICENSE_START(VERBATIM) |
| .\" Permission is granted to make and distribute verbatim copies of this |
| .\" manual provided the copyright notice and this permission notice are |
| .\" preserved on all copies. |
| .\" |
| .\" Permission is granted to copy and distribute modified versions of this |
| .\" manual under the conditions for verbatim copying, provided that the |
| .\" entire resulting derived work is distributed under the terms of a |
| .\" permission notice identical to this one. |
| .\" |
| .\" Since the Linux kernel and libraries are constantly changing, this |
| .\" manual page may be incorrect or out-of-date. The author(s) assume no |
| .\" responsibility for errors or omissions, or for damages resulting from |
| .\" the use of the information contained herein. The author(s) may not |
| .\" have taken the same level of care in the production of this manual, |
| .\" which is licensed free of charge, as they might when working |
| .\" professionally. |
| .\" |
| .\" Formatted or processed versions of this manual, if unaccompanied by |
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| .\" %%%LICENSE_END |
| .\" |
| .\" References consulted: |
| .\" Linux libc source code |
| .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) |
| .\" 386BSD man pages |
| .\" Modified Sat Jul 24 18:20:58 1993 by Rik Faith (faith@cs.unc.edu) |
| .\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl) |
| .\" Modified 9 Jun 2004, Michael Kerrisk <mtk.manpages@gmail.com> |
| .\" Changed unsetenv() prototype; added EINVAL error |
| .\" Noted nonstandard behavior of setenv() if name contains '=' |
| .\" 2005-08-12, mtk, glibc 2.3.4 fixed the "name contains '='" bug |
| .\" |
| .TH SETENV 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
| .SH NAME |
| setenv \- change or add an environment variable |
| .SH SYNOPSIS |
| .nf |
| .B #include <stdlib.h> |
| .PP |
| .BI "int setenv(const char *" name ", const char *" value ", int " overwrite ); |
| .BI "int unsetenv(const char *" name ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR setenv (), |
| .BR unsetenv (): |
| .nf |
| _POSIX_C_SOURCE >= 200112L |
| || /* Glibc <= 2.19: */ _BSD_SOURCE |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR setenv () |
| function adds the variable |
| .I name |
| to the |
| environment with the value |
| .IR value , |
| if |
| .I name |
| does not |
| already exist. |
| If |
| .I name |
| does exist in the environment, then |
| its value is changed to |
| .IR value |
| if |
| .I overwrite |
| is nonzero; |
| if |
| .IR overwrite |
| is zero, then the value of |
| .I name |
| is not changed (and |
| .BR setenv () |
| returns a success status). |
| This function makes copies of the strings pointed to by |
| .I name |
| and |
| .I value |
| (by contrast with |
| .BR putenv (3)). |
| .PP |
| The |
| .BR unsetenv () |
| function deletes the variable |
| .I name |
| from |
| the environment. |
| If |
| .I name |
| does not exist in the environment, |
| then the function succeeds, and the environment is unchanged. |
| .SH RETURN VALUE |
| .BR setenv () |
| and |
| .BR unsetenv () |
| functions return zero on success, |
| or \-1 on error, with |
| .I errno |
| set to indicate the error. |
| .SH ERRORS |
| .TP |
| .B EINVAL |
| .I name |
| is NULL, points to a string of length 0, |
| or contains an \(aq=\(aq character. |
| .TP |
| .B ENOMEM |
| Insufficient memory to add a new variable to the environment. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .ad l |
| .nh |
| .TS |
| allbox; |
| lbx lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR setenv (), |
| .BR unsetenv () |
| T} Thread safety MT-Unsafe const:env |
| .TE |
| .hy |
| .ad |
| .sp 1 |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008, 4.3BSD. |
| .SH NOTES |
| POSIX.1 does not require |
| .BR setenv () |
| or |
| .BR unsetenv () |
| to be reentrant. |
| .PP |
| Prior to glibc 2.2.2, |
| .BR unsetenv () |
| was prototyped |
| as returning |
| .IR void ; |
| more recent glibc versions follow the |
| POSIX.1-compliant prototype shown in the SYNOPSIS. |
| .SH BUGS |
| POSIX.1 specifies that if |
| .I name |
| contains an \(aq=\(aq character, then |
| .BR setenv () |
| should fail with the error |
| .BR EINVAL ; |
| however, versions of glibc before 2.3.4 allowed an \(aq=\(aq sign in |
| .IR name . |
| .SH SEE ALSO |
| .BR clearenv (3), |
| .BR getenv (3), |
| .BR putenv (3), |
| .BR environ (7) |
