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Diffstat (limited to 'usr.bin/env/env.1')
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diff --git a/usr.bin/env/env.1 b/usr.bin/env/env.1 new file mode 100644 index 0000000..101f4eb --- /dev/null +++ b/usr.bin/env/env.1 @@ -0,0 +1,482 @@ +.\" Copyright (c) 1980, 1990, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" This code is derived from software contributed to Berkeley by +.\" the Institute of Electrical and Electronics Engineers, Inc. +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" From @(#)printenv.1 8.1 (Berkeley) 6/6/93 +.\" From FreeBSD: src/usr.bin/printenv/printenv.1,v 1.17 2002/11/26 17:33:35 ru Exp +.\" $FreeBSD$ +.\" +.Dd April 17, 2008 +.Dt ENV 1 +.Os +.Sh NAME +.Nm env +.Nd set environment and execute command, or print environment +.Sh SYNOPSIS +.Nm +.Op Fl iv +.Op Fl P Ar altpath +.Op Fl S Ar string +.Op Fl u Ar name +.Op Ar name Ns = Ns Ar value ... +.Op Ar utility Op Ar argument ... +.Sh DESCRIPTION +The +.Nm +utility executes another +.Ar utility +after modifying the environment as +specified on the command line. +Each +.Ar name Ns = Ns Ar value +option specifies the setting of an environment variable, +.Ar name , +with a value of +.Ar value . +All such environment variables are set before the +.Ar utility +is executed. +.Pp +The options are as follows: +.Bl -tag -width indent +.It Fl i +Execute the +.Ar utility +with only those environment variables specified by +.Ar name Ns = Ns Ar value +options. +The environment inherited +by +.Nm +is ignored completely. +.\" -P +.It Fl P Ar altpath +Search the set of directories as specified by +.Ar altpath +to locate the specified +.Ar utility +program, instead of using the value of the +.Ev PATH +environment variable. +.\" -S +.It Fl S Ar string +Split apart the given +.Ar string +into multiple strings, and process each of the resulting strings +as separate arguments to the +.Nm +utility. +The +.Fl S +option recognizes some special character escape sequences and +also supports environment-variable substitution, as described +below. +.\" -u +.It Fl u Ar name +If the environment variable +.Ar name +is in the environment, then remove it before processing the +remaining options. +This is similar to the +.Ic unset +command in +.Xr sh 1 . +The value for +.Ar name +must not include the +.Ql = +character. +.\" -v +.It Fl v +Print verbose information for each step of processing done by the +.Nm +utility. +Additional information will be printed if +.Fl v +is specified multiple times. +.El +.Pp +The above options are only recognized when they are specified +before any +.Ar name Ns = Ns Ar value +options. +.Pp +If no +.Ar utility +is specified, +.Nm +prints out the names and values +of the variables in the environment, with one name/value pair per line. +.\" +.Ss Details of Fl S Ss (split-string) processing +The processing of the +.Fl S +option will split the given +.Ar string +into separate arguments based on any space or <tab> characters found in the +.Ar string . +Each of those new arguments will then be treated as if it had been +specified as a separate argument on the original +.Nm +command. +.Pp +Spaces and tabs may be embedded in one of those new arguments by using +single +.Pq Dq Li ' +or double +.Pq Ql \&" +quotes, or backslashes +.Pq Ql \e . +Single quotes will escape all non-single quote characters, up to +the matching single quote. +Double quotes will escape all non-double quote characters, up to +the matching double quote. +It is an error if the end of the +.Ar string +is reached before the matching quote character. +.Pp +If +.Fl S +would create a new argument that starts with the +.Ql # +character, then that argument and the remainder of the +.Ar string +will be ignored. +The +.Ql \e# +sequence can be used when you want a new argument to start +with a +.Ql # +character, without causing the remainder of the +.Ar string +to be skipped. +.Pp +While processing the +.Ar string +value, +.Fl S +processing will treat certain character combinations as escape +sequences which represent some action to take. +The character escape sequences are in backslash notation. +The characters and their meanings are as follows: +.Pp +.Bl -tag -width indent -offset indent -compact +.It Cm \ec +Ignore the remaining characters in the +.Ar string . +This must not appear inside a double-quoted string. +.It Cm \ef +Replace with a <form-feed> character. +.It Cm \en +Replace with a <new-line> character. +.It Cm \er +Replace with a <carriage return> character. +.It Cm \et +Replace with a <tab> character. +.It Cm \ev +Replace with a <vertical tab> character. +.It Cm \e# +Replace with a +.Ql # +character. +This would be useful when you need a +.Ql # +as the first character in one of the arguments created +by splitting apart the given +.Ar string . +.It Cm \e$ +Replace with a +.Ql $ +character. +.It Cm \e_ +If this is found inside of a double-quoted string, then replace it +with a single blank. +If this is found outside of a quoted string, then treat this as the +separator character between new arguments in the original +.Ar string . +.It Cm \e" +Replace with a <double quote> character. +.It Cm \e\' +Replace with a <single quote> character. +.It Cm \e\e +Replace with a backslash character. +.El +.Pp +The sequences for <single-quote> and backslash are the only sequences +which are recognized inside of a single-quoted string. +The other sequences have no special meaning inside a single-quoted +string. +All escape sequences are recognized inside of a double-quoted string. +It is an error if a single +.Ql \e +character is followed by a character other than the ones listed above. +.Pp +The processing of +.Fl S +also supports substitution of values from environment variables. +To do this, the name of the environment variable must be inside of +.Ql ${} , +such as: +.Li ${SOMEVAR} . +The common shell syntax of +.Li $SOMEVAR +is not supported. +All values substituted will be the values of the environment variables +as they were when the +.Nm +utility was originally invoked. +Those values will not be checked for any of the escape sequences as +described above. +And any settings of +.Ar name Ns = Ns Ar value +will not effect the values used for substitution in +.Fl S +processing. +.Pp +Also, +.Fl S +processing can not reference the value of the special parameters +which are defined by most shells. +For instance, +.Fl S +can not recognize special parameters such as: +.Ql $* , +.Ql $@ , +.Ql $# , +.Ql $? +or +.Ql $$ +if they appear inside the given +.Ar string . +.\" +.Ss Use in shell-scripts +The +.Nm +utility is often used as the +.Ar interpreter +on the first line of interpreted scripts, as +described in +.Xr execve 2 . +.Pp +Note that the way the kernel parses the +.Ql #! +(first line) of an interpreted script has changed as of +.Fx 6.0 . +Prior to that, the +.Fx +kernel would split that first line into separate arguments based +on any whitespace (space or <tab> characters) found in the line. +So, if a script named +.Pa /usr/local/bin/someport +had a first line of: +.Pp +.Dl "#!/usr/local/bin/php -n -q -dsafe_mode=0" +.Pp +then the +.Pa /usr/local/bin/php +program would have been started with the arguments of: +.Bd -literal -offset indent +arg[0] = '/usr/local/bin/php' +arg[1] = '-n' +arg[2] = '-q' +arg[3] = '-dsafe_mode=0' +arg[4] = '/usr/local/bin/someport' +.Ed +.Pp +plus any arguments the user specified when executing +.Pa someport . +However, this processing of multiple options on the +.Ql #! +line is not the way any other operating system parses the +first line of an interpreted script. +So after a change which was made for +.Fx 6.0 +release, that script will result in +.Pa /usr/local/bin/php +being started with the arguments of: +.Bd -literal -offset indent +arg[0] = '/usr/local/bin/php' +arg[1] = '-n -q -dsafe_mode=0' +arg[2] = '/usr/local/bin/someport' +.Ed +.Pp +plus any arguments the user specified. +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 +.Fx 6.0 +as it did under earlier releases, the first line should be +changed to: +.Pp +.Dl "#!/usr/bin/env -S /usr/local/bin/php -n -q -dsafe_mode=0" +.Pp +The +.Nm +utility will be started with the entire line as a single +argument: +.Pp +.Dl "arg[1] = '-S /usr/local/bin/php -n -q -dsafe_mode=0'" +.Pp +and then +.Fl S +processing will split that line into separate arguments before +executing +.Pa /usr/local/bin/php . +.\" +.Sh ENVIRONMENT +The +.Nm +utility uses the +.Ev PATH +environment variable to locate the requested +.Ar utility +if the name contains no +.Ql / +characters, unless the +.Fl P +option has been specified. +.Sh EXIT STATUS +.Ex -std +An exit status of 126 indicates that +.Ar utility +was found, but could not be executed. +An exit status of 127 indicates that +.Ar utility +could not be found. +.Sh EXAMPLES +Since the +.Nm +utility is often used as part of the first line of an interpreted script, +the following examples show a number of ways that the +.Nm +utility can be useful in scripts. +.Pp +The kernel processing of an interpreted script does not allow a script +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 +and +.Dl "#!/usr/bin/env /usr/local/bin/foo" +.Pp +is that the latter works even if +.Pa /usr/local/bin/foo +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 +is set to a value which will find the interpreter you want +to execute. +The +.Fl P +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 +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 +and +.Fl P +options: +.Pp +.Dl "#!/usr/bin/env -S-P/usr/local/bin:/usr/bin:${PATH} perl" +.Sh COMPATIBILITY +The +.Nm +utility accepts the +.Fl +option as a synonym for +.Fl i . +.Sh SEE ALSO +.Xr printenv 1 , +.Xr sh 1 , +.Xr execvp 3 , +.Xr environ 7 +.Sh STANDARDS +The +.Nm +utility conforms to +.St -p1003.1-2001 . +The +.Fl P , S , u +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 . +.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. |
