ENV(1)                       General Commands Manual                      ENV(1)

     env – set environment and execute command, or print environment

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

     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 specified
             by name=value options.  The environment inherited by env is ignored

     -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 remove
             it before processing the remaining options.  This is similar to the
             unset command in sh(1).  The value for name must not include 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 specified 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
     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:

           \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 arguments
                   created by splitting apart the given string.
           \$      Replace with a ‘$’ character.
           \_      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 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 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
     ‘\’ character is followed by a character other than the ones listed above.

     The processing of -S also supports substitution of values from environment
     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 originally 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
     interpreted scripts, as described in execve(2).

     Note that the way the kernel parses the ‘#!’ (first line) of an interpreted
     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
     arguments 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 releases, 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 argument:

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

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

     The env utility uses the PATH environment variable to locate the requested
     utility if the name contains no ‘/’ characters, unless the -P option has
     been specified.

     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 executed.
     An exit status of 127 indicates that utility could not be found.

     Since the env utility is often used as part of the first line of an
     interpreted 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/bin/env /usr/local/bin/foo

     is that the latter works even if /usr/local/bin/foo is itself an
     interpreted 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’ interpreter 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 execute.  The
     -P option can be used to make sure a specific list of directories 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
     flexibility.  Note that spaces are not required between the -S and -P

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

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

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

     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.

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

     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
     processing the -S option, which may lead to incorrect results in some

macOS 12.1                       April 17, 2008                       macOS 12.1