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adeca21464
Add mostly glibc and msl compatible secure_getenv. Return NULL if issetugid() indicates the process is tainted, otherwise getenv(x). The rational behind this is the fact that many Linux applications use this function instead of getenv() as it's widely consider a, "best practice". Reviewed by: imp, mjg (feedback) Pull Request: https://github.com/freebsd/freebsd-src/pull/686 Signed-off-by: Lucy Marsh <seafork@disroot.org>
270 lines
6 KiB
Groff
270 lines
6 KiB
Groff
.\" Copyright (c) 1988, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
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.\" $FreeBSD$
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.\"
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.Dd March 13, 2023
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.Dt GETENV 3
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.Os
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.Sh NAME
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.Nm clearenv ,
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.Nm getenv ,
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.Nm putenv ,
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.Nm secure_getenv ,
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.Nm setenv ,
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.Nm unsetenv
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.Nd environment variable functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.Ft int
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.Fn clearenv "void"
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.Ft char *
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.Fn getenv "const char *name"
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.Ft char *
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.Fn secure_getenv "const char *name"
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.Ft int
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.Fn setenv "const char *name" "const char *value" "int overwrite"
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.Ft int
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.Fn putenv "char *string"
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.Ft int
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.Fn unsetenv "const char *name"
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.Sh DESCRIPTION
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These functions set, unset and fetch environment variables from the
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host
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.Em environment list .
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.Pp
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The
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.Fn clearenv
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function clears all environment variables.
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New variables can be added using
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.Fn setenv
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and
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.Fn putenv .
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.Pp
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The
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.Fn getenv
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function obtains the current value of the environment variable,
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.Fa name .
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The application should not modify the string pointed
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to by the
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.Fn getenv
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function.
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.Pp
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The GNU-specific function,
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.Fn secure_getenv
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wraps the
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.Fn getenv
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function to prevent it from being run in "secure execution".
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Unlike in glibc,
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.Fn secure_getenv
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only checks if the
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.Fa setuid
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and
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.Fa setgid
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bits have been set or changed.
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These checks are subject to extension and change.
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.Pp
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The
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.Fn setenv
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function inserts or resets the environment variable
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.Fa name
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in the current environment list.
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If the variable
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.Fa name
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does not exist in the list,
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it is inserted with the given
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.Fa value .
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If the variable does exist, the argument
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.Fa overwrite
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is tested; if
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.Fa overwrite
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is zero, the
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variable is not reset, otherwise it is reset
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to the given
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.Fa value .
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.Pp
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The
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.Fn putenv
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function takes an argument of the form ``name=value'' and
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puts it directly into the current environment,
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so altering the argument shall change the environment.
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If the variable
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.Fa name
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does not exist in the list,
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it is inserted with the given
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.Fa value .
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If the variable
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.Fa name
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does exist, it is reset to the given
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.Fa value .
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.Pp
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The
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.Fn unsetenv
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function
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deletes all instances of the variable name pointed to by
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.Fa name
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from the list.
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.Pp
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If corruption (e.g., a name without a value) is detected while making a copy of
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environ for internal usage, then
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.Fn setenv ,
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.Fn unsetenv
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and
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.Fn putenv
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will output a warning to stderr about the issue, drop the corrupt entry and
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complete the task without error.
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.Sh RETURN VALUES
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The
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.Fn getenv
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function returns the value of the environment variable as a
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.Dv NUL Ns
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-terminated string.
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If the variable
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.Fa name
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is not in the current environment,
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.Dv NULL
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is returned.
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.Pp
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The
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.Fn secure_getenv
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function returns
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.Dv NULL
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if the process is in "secure execution," otherwise it will call
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.Fn getenv .
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.Pp
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.Rv -std clearenv setenv putenv unsetenv
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The function
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.Fn getenv ,
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.Fn setenv
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or
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.Fn unsetenv
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failed because the
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.Fa name
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is a
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.Dv NULL
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pointer, points to an empty string, or points to a string containing an
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.Dq Li \&=
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character.
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.Pp
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The function
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.Fn putenv
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failed because
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.Fa string
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is a
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.Dv NULL
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pointer,
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.Fa string
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is without an
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.Dq Li \&=
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character or
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.Dq Li \&=
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is the first character in
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.Fa string .
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This does not follow the
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.Tn POSIX
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specification.
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.It Bq Er ENOMEM
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The function
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.Fn setenv ,
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.Fn unsetenv
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or
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.Fn putenv
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failed because they were unable to allocate memory for the environment.
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.El
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.Sh SEE ALSO
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.Xr csh 1 ,
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.Xr sh 1 ,
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.Xr execve 2 ,
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.Xr environ 7
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.Sh STANDARDS
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The
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.Fn getenv
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function conforms to
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.St -isoC .
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The
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.Fn setenv ,
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.Fn putenv
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and
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.Fn unsetenv
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functions conforms to
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.St -p1003.1-2001 .
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.Sh HISTORY
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The functions
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.Fn setenv
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and
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.Fn unsetenv
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appeared in
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.At v7 .
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The
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.Fn putenv
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function appeared in
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.Bx 4.3 Reno .
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.Pp
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Until
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.Fx 7.0 ,
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.Fn putenv
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would make a copy of
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.Fa string
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and insert it into the environment using
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.Fn setenv .
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This was changed to use
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.Fa string
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as the memory location of the ``name=value'' pair to follow the
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.Tn POSIX
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specification.
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.Pp
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The
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.Fn clearenv
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was added in
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.Fx 14 .
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.Sh BUGS
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Successive calls to
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.Fn setenv
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that assign a larger-sized
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.Fa value
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than any previous value to the same
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.Fa name
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will result in a memory leak.
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The
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.Fx
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semantics for this function
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(namely, that the contents of
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.Fa value
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are copied and that old values remain accessible indefinitely) make this
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bug unavoidable.
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Future versions may eliminate one or both of these
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semantic guarantees in order to fix the bug.
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