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531 lines
13 KiB
Groff
531 lines
13 KiB
Groff
.\" Copyright (c) 1980, 1990, 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 Institute of Electrical and Electronics Engineers, Inc.
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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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.\" From @(#)printenv.1 8.1 (Berkeley) 6/6/93
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.\" From FreeBSD: src/usr.bin/printenv/printenv.1,v 1.17 2002/11/26 17:33:35 ru Exp
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.\"
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.Dd March 3, 2021
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.Dt ENV 1
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.Os
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.Sh NAME
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.Nm env
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.Nd set environment and execute command, or print environment
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.Sh SYNOPSIS
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.Nm
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.Op Fl 0iv
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.Op Fl L Ns | Ns Fl U Ar user Ns Op / Ns Ar class
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.Op Fl u Ar name
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.Op Ar name Ns = Ns Ar value ...
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.Nm
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.Op Fl iv
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.Op Fl L Ns | Ns Fl U Ar user Ns Op / Ns Ar class
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.Op Fl P Ar altpath
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.Op Fl S Ar string
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.Op Fl u Ar name
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.Op Ar name Ns = Ns Ar value ...
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.Ar utility Op Ar argument ...
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.Sh DESCRIPTION
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The
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.Nm
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utility executes another
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.Ar utility
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after modifying the environment as
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specified on the command line.
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Each
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.Ar name Ns = Ns Ar value
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option specifies the setting of an environment variable,
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.Ar name ,
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with a value of
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.Ar value .
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All such environment variables are set before the
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.Ar utility
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is executed.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl 0
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End each output line with NUL, not newline.
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.It Fl i
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Execute the
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.Ar utility
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with only those environment variables specified by
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.Ar name Ns = Ns Ar value
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options.
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The environment inherited
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by
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.Nm
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is ignored completely.
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.\" -L | -U
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.It Fl L | Fl U Ar user Ns Op / Ns Ar class
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Add the environment variable definitions from
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.Xr login.conf 5
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for the specified user and login class to the environment, after
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processing any
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.Fl i
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or
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.Fl u
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options, but before processing any
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.Ar name Ns = Ns Ar value
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options.
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If
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.Fl L
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is used, only the system-wide
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.Pa /etc/login.conf.db
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file is read; if
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.Fl U
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is used, then the specified user's
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.Pa ~/.login_conf
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is read as well.
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The user may be specified by name or by uid.
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If a username of
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.Sq Li \&-
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is given, then no user lookup will be done, the login class will default to
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.Sq Li default
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if not explicitly given, and no substitutions will be done on the values.
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.\" -P
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.It Fl P Ar altpath
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Search the set of directories as specified by
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.Ar altpath
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to locate the specified
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.Ar utility
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program, instead of using the value of the
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.Ev PATH
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environment variable.
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.\" -S
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.It Fl S Ar string
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Split apart the given
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.Ar string
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into multiple strings, and process each of the resulting strings
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as separate arguments to the
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.Nm
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utility.
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The
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.Fl S
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option recognizes some special character escape sequences and
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also supports environment-variable substitution, as described
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below.
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.\" -u
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.It Fl u Ar name
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If the environment variable
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.Ar name
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is in the environment, then remove it before processing the
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remaining options.
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This is similar to the
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.Ic unset
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command in
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.Xr sh 1 .
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The value for
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.Ar name
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must not include the
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.Ql =
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character.
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.\" -v
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.It Fl v
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Print verbose information for each step of processing done by the
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.Nm
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utility.
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Additional information will be printed if
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.Fl v
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is specified multiple times.
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.El
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.Pp
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The above options are only recognized when they are specified
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before any
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.Ar name Ns = Ns Ar value
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options.
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.Pp
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If no
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.Ar utility
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is specified,
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.Nm
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prints out the names and values of the variables in the environment.
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Each name/value pair is separated by a new line unless
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.Fl 0
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is specified, in which case name/value pairs are separated by NUL.
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Both
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.Fl 0
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and
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.Ar utility
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may not be specified together.
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.\"
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.Ss Details of -S (split-string) processing
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The processing of the
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.Fl S
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option will split the given
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.Ar string
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into separate arguments based on any space or <tab> characters found in the
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.Ar string .
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Each of those new arguments will then be treated as if it had been
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specified as a separate argument on the original
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.Nm
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command.
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.Pp
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Spaces and tabs may be embedded in one of those new arguments by using
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single
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.Pq Dq Li '
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or double
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.Pq Ql \&"
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quotes, or backslashes
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.Pq Ql \e .
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Single quotes will escape all non-single quote characters, up to
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the matching single quote.
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Double quotes will escape all non-double quote characters, up to
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the matching double quote.
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It is an error if the end of the
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.Ar string
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is reached before the matching quote character.
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.Pp
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If
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.Fl S
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would create a new argument that starts with the
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.Ql #
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character, then that argument and the remainder of the
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.Ar string
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will be ignored.
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The
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.Ql \e#
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sequence can be used when you want a new argument to start
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with a
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.Ql #
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character, without causing the remainder of the
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.Ar string
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to be skipped.
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.Pp
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While processing the
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.Ar string
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value,
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.Fl S
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processing will treat certain character combinations as escape
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sequences which represent some action to take.
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The character escape sequences are in backslash notation.
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The characters and their meanings are as follows:
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.Pp
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.Bl -tag -width indent -offset indent -compact
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.It Cm \ec
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Ignore the remaining characters in the
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.Ar string .
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This must not appear inside a double-quoted string.
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.It Cm \ef
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Replace with a <form-feed> character.
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.It Cm \en
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Replace with a <new-line> character.
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.It Cm \er
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Replace with a <carriage return> character.
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.It Cm \et
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Replace with a <tab> character.
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.It Cm \ev
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Replace with a <vertical tab> character.
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.It Cm \e#
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Replace with a
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.Ql #
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character.
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|
This would be useful when you need a
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.Ql #
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as the first character in one of the arguments created
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by splitting apart the given
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.Ar string .
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|
.It Cm \e$
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Replace with a
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.Ql $
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character.
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.It Cm \e_
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If this is found inside of a double-quoted string, then replace it
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with a single blank.
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If this is found outside of a quoted string, then treat this as the
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separator character between new arguments in the original
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.Ar string .
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|
.It Cm \e"
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|
Replace with a <double quote> character.
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.It Cm \e\'
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Replace with a <single quote> character.
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.It Cm \e\e
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Replace with a backslash character.
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.El
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.Pp
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|
The sequences for <single-quote> and backslash are the only sequences
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which are recognized inside of a single-quoted string.
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The other sequences have no special meaning inside a single-quoted
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string.
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|
All escape sequences are recognized inside of a double-quoted string.
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|
It is an error if a single
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.Ql \e
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|
character is followed by a character other than the ones listed above.
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.Pp
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|
The processing of
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.Fl S
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|
also supports substitution of values from environment variables.
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|
To do this, the name of the environment variable must be inside of
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.Ql ${} ,
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|
such as:
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.Li ${SOMEVAR} .
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|
The common shell syntax of
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.Li $SOMEVAR
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is not supported.
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All values substituted will be the values of the environment variables
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as they were when the
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.Nm
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utility was originally invoked.
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Those values will not be checked for any of the escape sequences as
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described above.
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And any settings of
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.Ar name Ns = Ns Ar value
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will not effect the values used for substitution in
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.Fl S
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processing.
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.Pp
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Also,
|
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.Fl S
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processing cannot reference the value of the special parameters
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which are defined by most shells.
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For instance,
|
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.Fl S
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|
cannot recognize special parameters such as:
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.Ql $* ,
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.Ql $@ ,
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|
.Ql $# ,
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|
.Ql $?
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or
|
|
.Ql $$
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if they appear inside the given
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.Ar string .
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.\"
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.Ss Use in shell-scripts
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The
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.Nm
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utility is often used as the
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.Ar interpreter
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on the first line of interpreted scripts, as
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described in
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.Xr execve 2 .
|
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.Pp
|
|
Note that the way the kernel parses the
|
|
.Ql #!
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(first line) of an interpreted script has changed as of
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.Fx 6.0 .
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|
Prior to that, the
|
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.Fx
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|
kernel would split that first line into separate arguments based
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on any whitespace (space or <tab> characters) found in the line.
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|
So, if a script named
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.Pa /usr/local/bin/someport
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had a first line of:
|
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.Pp
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.Dl "#!/usr/local/bin/php -n -q -dsafe_mode=0"
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.Pp
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|
then the
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.Pa /usr/local/bin/php
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program would have been started with the arguments of:
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.Bd -literal -offset indent
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arg[0] = '/usr/local/bin/php'
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arg[1] = '-n'
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arg[2] = '-q'
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arg[3] = '-dsafe_mode=0'
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arg[4] = '/usr/local/bin/someport'
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.Ed
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.Pp
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|
plus any arguments the user specified when executing
|
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.Pa someport .
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However, this processing of multiple options on the
|
|
.Ql #!
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line is not the way any other operating system parses the
|
|
first line of an interpreted script.
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So after a change which was made for
|
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.Fx 6.0
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release, that script will result in
|
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.Pa /usr/local/bin/php
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being started with the arguments of:
|
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.Bd -literal -offset indent
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arg[0] = '/usr/local/bin/php'
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arg[1] = '-n -q -dsafe_mode=0'
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arg[2] = '/usr/local/bin/someport'
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.Ed
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.Pp
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plus any arguments the user specified.
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This caused a significant change in the behavior of a few scripts.
|
|
In the case of above script, to have it behave the same way under
|
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.Fx 6.0
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as it did under earlier releases, the first line should be
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changed to:
|
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.Pp
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.Dl "#!/usr/bin/env -S /usr/local/bin/php -n -q -dsafe_mode=0"
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.Pp
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The
|
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.Nm
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utility will be started with the entire line as a single
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argument:
|
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.Pp
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.Dl "arg[1] = '-S /usr/local/bin/php -n -q -dsafe_mode=0'"
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.Pp
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and then
|
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.Fl S
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|
processing will split that line into separate arguments before
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executing
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.Pa /usr/local/bin/php .
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.\"
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.Sh ENVIRONMENT
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The
|
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.Nm
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utility uses the
|
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.Ev PATH
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environment variable to locate the requested
|
|
.Ar utility
|
|
if the name contains no
|
|
.Ql /
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characters, unless the
|
|
.Fl P
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option has been specified.
|
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.Sh EXIT STATUS
|
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.Ex -std
|
|
An exit status of 126 indicates that
|
|
.Ar utility
|
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was found, but could not be executed.
|
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An exit status of 127 indicates that
|
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.Ar utility
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could not be found.
|
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.Sh EXAMPLES
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Since the
|
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.Nm
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utility is often used as part of the first line of an interpreted script,
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the following examples show a number of ways that the
|
|
.Nm
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utility can be useful in scripts.
|
|
.Pp
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|
The kernel processing of an interpreted script does not allow a script
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|
to directly reference some other script as its own interpreter.
|
|
As a way around this, the main difference between
|
|
.Pp
|
|
.Dl #!/usr/local/bin/foo
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|
and
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|
.Dl "#!/usr/bin/env /usr/local/bin/foo"
|
|
.Pp
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|
is that the latter works even if
|
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.Pa /usr/local/bin/foo
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|
is itself an interpreted script.
|
|
.Pp
|
|
Probably the most common use of
|
|
.Nm
|
|
is to find the correct interpreter for a script, when the interpreter
|
|
may be in different directories on different systems.
|
|
The following example will find the
|
|
.Ql perl
|
|
interpreter by searching through the directories specified by
|
|
.Ev PATH .
|
|
.Pp
|
|
.Dl "#!/usr/bin/env perl"
|
|
.Pp
|
|
One limitation of that example is that it assumes the user's value
|
|
for
|
|
.Ev PATH
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|
is set to a value which will find the interpreter you want
|
|
to execute.
|
|
The
|
|
.Fl P
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|
option can be used to make sure a specific list of directories is
|
|
used in the search for
|
|
.Ar utility .
|
|
Note that the
|
|
.Fl S
|
|
option is also required for this example to work correctly.
|
|
.Pp
|
|
.Dl "#!/usr/bin/env -S -P/usr/local/bin:/usr/bin perl"
|
|
.Pp
|
|
The above finds
|
|
.Ql perl
|
|
only if it is in
|
|
.Pa /usr/local/bin
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|
or
|
|
.Pa /usr/bin .
|
|
That could be combined with the present value of
|
|
.Ev PATH ,
|
|
to provide more flexibility.
|
|
Note that spaces are not required between the
|
|
.Fl S
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|
and
|
|
.Fl P
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|
options:
|
|
.Pp
|
|
.Dl "#!/usr/bin/env -S-P/usr/local/bin:/usr/bin:${PATH} perl"
|
|
.Sh COMPATIBILITY
|
|
The
|
|
.Nm
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|
utility accepts the
|
|
.Fl
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|
option as a synonym for
|
|
.Fl i .
|
|
.Sh SEE ALSO
|
|
.Xr printenv 1 ,
|
|
.Xr sh 1 ,
|
|
.Xr execvp 3 ,
|
|
.Xr login.conf 5 ,
|
|
.Xr environ 7
|
|
.Sh STANDARDS
|
|
The
|
|
.Nm
|
|
utility conforms to
|
|
.St -p1003.1-2001 .
|
|
The
|
|
.Fl 0 , L , P , S , U , u
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|
and
|
|
.Fl v
|
|
options are non-standard extensions supported by
|
|
.Fx ,
|
|
but which may not be available on other operating systems.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
command appeared in
|
|
.Bx 4.4 .
|
|
The
|
|
.Fl P , S
|
|
and
|
|
.Fl v
|
|
options were added in
|
|
.Fx 6.0 .
|
|
The
|
|
.Fl 0 , L
|
|
and
|
|
.Fl U
|
|
options were added in
|
|
.Fx 13.0 .
|
|
.Sh BUGS
|
|
The
|
|
.Nm
|
|
utility does not handle values of
|
|
.Ar utility
|
|
which have an equals sign
|
|
.Pq Ql =
|
|
in their name, for obvious reasons.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
utility does not take multibyte characters into account when
|
|
processing the
|
|
.Fl S
|
|
option, which may lead to incorrect results in some locales.
|