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ENV(1)			  BSD General Commands Manual			ENV(1)

NAME
     env -- set	environment and	execute	command, or print environment

SYNOPSIS
     env [-iv] [-P altpath] [-S	string]	[-u name] [name=value ...]
	 [utility [argument ...]]

DESCRIPTION
     The env utility executes another utility after modifying the environment
     as	specified on the command line.	Each name=value	option specifies the
     setting of	an environment variable, name, with a value of value.  All
     such environment variables	are set	before the utility is executed.

     The options are as	follows:

     -i	     Execute the utility with only those environment variables speci-
	     fied by name=value	options.  The environment inherited by env is
	     ignored completely.

     -P	altpath
	     Search the	set of directories as specified	by altpath to locate
	     the specified utility program, instead of using the value of the
	     PATH environment variable.

     -S	string
	     Split apart the given string into multiple	strings, and process
	     each of the resulting strings as separate arguments to the	env
	     utility.  The -S option recognizes	some special character escape
	     sequences and also	supports environment-variable substitution, as
	     described below.

     -u	name
	     If	the environment	variable name is in the	environment, then re-
	     move it before processing the remaining options.  This is similar
	     to	the unset command in sh(1).  The value for name	must not in-
	     clude the `=' character.

     -v	     Print verbose information for each	step of	processing done	by the
	     env utility.  Additional information will be printed if -v	is
	     specified multiple	times.

     The above options are only	recognized when	they are specified before any
     name=value	options.

     If	no utility is specified, env prints out	the names and values of	the
     variables in the environment, with	one name/value pair per	line.

   Details of -S -Ss -(split-string) -processing
     The processing of the -S option will split	the given string into separate
     arguments based on	any space or <tab> characters found in the string.
     Each of those new arguments will then be treated as if it had been	speci-
     fied as a separate	argument on the	original env command.

     Spaces and	tabs may be embedded in	one of those new arguments by using
     single ("'") or double (`"') quotes, or backslashes (`\').	 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 string is
     reached before the	matching quote character.

     If	-S would create	a new argument that starts with	the `#'	character,
     then that argument	and the	remainder of the string	will be	ignored.  The
     `\#' sequence can be used when you	want a new argument to start with a
     `#' character, without causing the	remainder of the string	to be skipped.

     While processing the string value,	-S processing will treat certain char-
     acter 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:

	   \c	   Ignore the remaining	characters in the string.  This	must
		   not appear inside a double-quoted string.
	   \f	   Replace with	a <form-feed> character.
	   \n	   Replace with	a <new-line> character.
	   \r	   Replace with	a <carriage return> character.
	   \t	   Replace with	a <tab>	character.
	   \v	   Replace with	a <vertical tab> character.
	   \#	   Replace with	a `#' character.  This would be	useful when
		   you need a `#' as the first character in one	of the argu-
		   ments created by splitting apart the	given string.
	   \$	   Replace with	a `$' character.
	   \_	   If this is found inside of a	double-quoted string, then re-
		   place 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 string.
	   \"	   Replace with	a <double quote> character.
	   \'	   Replace with	a <single quote> character.
	   \\	   Replace with	a backslash character.

     The sequences for <single-quote> and backslash are	the only sequences
     which are recognized inside of a single-quoted string.  The other se-
     quences have no special meaning inside a single-quoted string.  All es-
     cape sequences are	recognized inside of a double-quoted string.  It is an
     error if a	single `\' character is	followed by a character	other than the
     ones listed above.

     The processing of -S also supports	substitution of	values from environ-
     ment variables.  To do this, the name of the environment variable must be
     inside of `${}', such as: ${SOMEVAR}.  The	common shell syntax of
     $SOMEVAR is not supported.	 All values substituted	will be	the values of
     the environment variables as they were when the env utility was origi-
     nally invoked.  Those values will not be checked for any of the escape
     sequences as described above.  And	any settings of	name=value will	not
     effect the	values used for	substitution in	-S processing.

     Also, -S processing can not reference the value of	the special parameters
     which are defined by most shells.	For instance, -S can not recognize
     special parameters	such as: `$*', `$@', `$#', `$?'	or `$$'	if they	appear
     inside the	given string.

   Use in shell-scripts
     The env utility is	often used as the interpreter on the first line	of in-
     terpreted scripts,	as described in	execve(2).

     Note that the way the kernel parses the `#!' (first line) of an inter-
     preted script has changed as of FreeBSD 6.0.  Prior to that, the FreeBSD
     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 /usr/local/bin/someport had a	first line of:

	   #!/usr/local/bin/php	-n -q -dsafe_mode=0

     then the /usr/local/bin/php program would have been started with the ar-
     guments of:

	   arg[0] = '/usr/local/bin/php'
	   arg[1] = '-n'
	   arg[2] = '-q'
	   arg[3] = '-dsafe_mode=0'
	   arg[4] = '/usr/local/bin/someport'

     plus any arguments	the user specified when	executing someport.  However,
     this processing of	multiple options on the	`#!' 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 FreeBSD 6.0 release, that script
     will result in /usr/local/bin/php being started with the arguments	of:

	   arg[0] = '/usr/local/bin/php'
	   arg[1] = '-n	-q -dsafe_mode=0'
	   arg[2] = '/usr/local/bin/someport'

     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 FreeBSD 6.0 as it did	under earlier re-
     leases, the first line should be changed to:

	   #!/usr/bin/env -S /usr/local/bin/php	-n -q -dsafe_mode=0

     The env utility will be started with the entire line as a single argu-
     ment:

	   arg[1] = '-S	/usr/local/bin/php -n -q -dsafe_mode=0'

     and then -S processing will split that line into separate arguments be-
     fore executing /usr/local/bin/php.

ENVIRONMENT
     The env utility uses the PATH environment variable	to locate the re-
     quested utility if	the name contains no `/' characters, unless the	-P op-
     tion has been specified.

EXIT STATUS
     The env utility exits 0 on	success, and >0	if an error occurs.  An	exit
     status of 126 indicates that utility was found, but could not be exe-
     cuted.  An	exit status of 127 indicates that utility could	not be found.

EXAMPLES
     Since the env utility is often used as part of the	first line of an in-
     terpreted script, the following examples show a number of ways that the
     env utility can be	useful in scripts.

     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

	   #!/usr/local/bin/foo
     and
	   #!/usr/bin/env /usr/local/bin/foo

     is	that the latter	works even if /usr/local/bin/foo is itself an inter-
     preted script.

     Probably the most common use of env 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 `perl' inter-
     preter by searching through the directories specified by PATH.

	   #!/usr/bin/env perl

     One limitation of that example is that it assumes the user's value	for
     PATH is set to a value which will find the	interpreter you	want to	exe-
     cute.  The	-P option can be used to make sure a specific list of directo-
     ries is used in the search	for utility.  Note that	the -S option is also
     required for this example to work correctly.

	   #!/usr/bin/env -S -P/usr/local/bin:/usr/bin perl

     The above finds `perl' only if it is in /usr/local/bin or /usr/bin.  That
     could be combined with the	present	value of PATH, to provide more flexi-
     bility.  Note that	spaces are not required	between	the -S and -P options:

	   #!/usr/bin/env -S-P/usr/local/bin:/usr/bin:${PATH} perl

COMPATIBILITY
     The env utility accepts the - option as a synonym for -i.

SEE ALSO
     printenv(1), sh(1), execvp(3), environ(7)

STANDARDS
     The env utility conforms to IEEE Std 1003.1-2001 ("POSIX.1").  The	-P,
     -S, -u and	-v options are non-standard extensions supported by FreeBSD,
     but which may not be available on other operating systems.

HISTORY
     The env command appeared in 4.4BSD.  The -P, -S and -v options were added
     in	FreeBSD	6.0.

BUGS
     The env utility does not handle values of utility which have an equals
     sign (`=')	in their name, for obvious reasons.

     The env utility does not take multibyte characters	into account when pro-
     cessing the -S option, which may lead to incorrect	results	in some	lo-
     cales.

BSD				April 17, 2008				   BSD

NAME | SYNOPSIS | DESCRIPTION | ENVIRONMENT | EXIT STATUS | EXAMPLES | COMPATIBILITY | SEE ALSO | STANDARDS | HISTORY | BUGS

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