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.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Single UNIX Specification, Version 2
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.\" Modified Thu Apr 8 15:00:12 1993, David Metcalfe
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.\" Modified Sat Jul 24 18:44:45 1993, Rik Faith (faith@cs.unc.edu)
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.\" Modified Fri Feb 14 21:47:50 1997 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified Mon Oct 11 11:11:11 1999 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified Wed Nov 10 00:02:26 1999 by Andries Brouwer (aeb@cwi.nl)
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.\" Modified Sun May 20 22:17:20 2001 by Andries Brouwer (aeb@cwi.nl)
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2007-07-08 12:11:40 +00:00
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.TH PUTENV 3 2007-07-26 "GNU" "Linux Programmer's Manual"
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.SH NAME
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putenv \- change or add an environment variable
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.SH SYNOPSIS
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.nf
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.B #include <stdlib.h>
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.sp
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.BI "int putenv(char *" string );
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.\" Not: const char *
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR putenv ():
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_SVID_SOURCE || _XOPEN_SOURCE
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.SH DESCRIPTION
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2007-05-12 09:06:04 +00:00
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The
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.BR putenv ()
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function adds or changes the value of environment
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variables.
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The argument \fIstring\fP is of the form \fIname\fP=\fIvalue\fP.
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If \fIname\fP does not already exist in the environment, then
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\fIstring\fP is added to the environment.
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If \fIname\fP does exist,
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then the value of \fIname\fP in the environment is changed to
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\fIvalue\fP.
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The string pointed to by \fIstring\fP becomes part of the environment,
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so altering the string changes the environment.
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.SH "RETURN VALUE"
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2007-05-12 09:06:04 +00:00
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The
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.BR putenv ()
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function returns zero on success,
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intro.1, time.1, adjtimex.2, capget.2, eventfd.2, fcntl.2, getrlimit.2, getsockopt.2, gettimeofday.2, intro.2, ioctl_list.2, ioperm.2, mlock.2, pivot_root.2, poll.2, prctl.2, ptrace.2, sched_setscheduler.2, select_tut.2, semget.2, sigaltstack.2, signalfd.2, sysctl.2, timer_settime.2, timerfd_create.2, wait.2, CPU_SET.3, argz_add.3, assert_perror.3, atexit.3, backtrace.3, bcmp.3, clearenv.3, ctime.3, dl_iterate_phdr.3, dlopen.3, ecvt.3, errno.3, error.3, ether_aton.3, exit.3, fenv.3, ferror.3, finite.3, flockfile.3, fnmatch.3, fpathconf.3, fpclassify.3, ftime.3, ftok.3, ftw.3, fwide.3, getaddrinfo.3, gethostbyname.3, getlogin.3, getnameinfo.3, getnetent.3, getopt.3, getprotoent.3, getrpcent.3, getservent.3, glob.3, hsearch.3, inet.3, isalpha.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, longjmp.3, lsearch.3, malloc.3, matherr.3, mblen.3, mbsinit.3, mbtowc.3, on_exit.3, printf.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_attr_setdetachstate.3, pthread_attr_setguardsize.3, pthread_attr_setinheritsched.3, pthread_attr_setschedparam.3, pthread_attr_setschedpolicy.3, pthread_attr_setscope.3, pthread_attr_setstack.3, pthread_attr_setstackaddr.3, pthread_attr_setstacksize.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_equal.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setschedparam.3, pthread_setschedprio.3, ptsname.3, putenv.3, putgrent.3, raise.3, rcmd.3, regex.3, rexec.3, rpc.3, rpmatch.3, rtnetlink.3, scandir.3, sem_init.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, signbit.3, stdio_ext.3, strtod.3, strtol.3, strtoul.3, system.3, termios.3, timeradd.3, tzset.3, ualarm.3, wctomb.3, xdr.3, st.4, tty_ioctl.4, core.5, elf.5, proc.5, bootparam.7, capabilities.7, icmp.7, ip.7, ipv6.7, math_error.7, mdoc.samples.7, mq_overview.7, pthreads.7, raw.7, regex.7, socket.7, tcp.7, tzselect.8: Global fix: s/non-zero/nonzero/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:40:55 +00:00
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or nonzero if an error occurs.
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.SH ERRORS
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.TP
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.B ENOMEM
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Insufficient space to allocate new environment.
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2007-05-19 04:30:20 +00:00
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.SH "CONFORMING TO"
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2008-07-15 13:39:17 +00:00
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SVr4, POSIX.1-2001, 4.3BSD.
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.SH NOTES
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2007-05-12 09:06:04 +00:00
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The
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.BR putenv ()
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function is not required to be reentrant, and the
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2007-05-16 04:00:06 +00:00
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one in libc4, libc5 and glibc 2.0 is not, but the glibc 2.1 version is.
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.LP
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Description for libc4, libc5, glibc:
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If the argument \fIstring\fP is of the form \fIname\fP,
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and does not contain an \(aq=\(aq character, then the variable \fIname\fP
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is removed from the environment.
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If
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.BR putenv ()
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has to allocate a new array \fIenviron\fP,
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and the previous array was also allocated by
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.BR putenv (),
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then it will be freed.
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In no case will the old storage associated
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to the environment variable itself be freed.
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.LP
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The libc4 and libc5 and glibc 2.1.2 versions conform to SUSv2:
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the pointer \fIstring\fP given to
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.BR putenv ()
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is used.
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In particular, this string becomes part of the environment;
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changing it later will change the environment.
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2007-05-12 09:06:04 +00:00
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(Thus, it is an error is to call
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.BR putenv ()
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with an automatic variable
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as the argument, then return from the calling function while \fIstring\fP
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is still part of the environment.)
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However, glibc 2.0-2.1.1 differs: a copy of the string is used.
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On the one hand this causes a memory leak, and on the other hand
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it violates SUSv2.
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2007-04-21 11:05:12 +00:00
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This has been fixed in glibc 2.1.2.
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2004-11-03 13:51:07 +00:00
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.LP
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2005-07-18 15:05:56 +00:00
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The 4.4BSD version, like glibc 2.0, uses a copy.
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2004-11-03 13:51:07 +00:00
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.LP
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2007-06-12 21:19:16 +00:00
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SUSv2 removes the \fIconst\fP from the prototype, and so does glibc 2.1.3.
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2004-11-03 13:51:07 +00:00
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.SH "SEE ALSO"
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.BR clearenv (3),
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.BR getenv (3),
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.BR setenv (3),
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.BR unsetenv (3),
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2006-04-21 00:45:46 +00:00
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.BR environ (7)
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