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30 .\" From @(#)printenv.1 8.1 (Berkeley) 6/6/93
31 .\" From FreeBSD: src/usr.bin/printenv/printenv.1,v 1.17 2002/11/26 17:33:35 ru Exp
39 .Nd set environment and execute command, or print environment
46 .Op Ar name Ns = Ns Ar value ...
47 .Op Ar utility Op Ar argument ...
51 utility executes another
53 after modifying the environment as
54 specified on the command line.
56 .Ar name Ns = Ns Ar value
57 option specifies the setting of an environment variable,
61 All such environment variables are set before the
65 The options are as follows:
66 .Bl -tag -width indent
68 End each output line with NUL, not newline.
72 with only those environment variables specified by
73 .Ar name Ns = Ns Ar value
75 The environment inherited
78 is ignored completely.
81 Search the set of directories as specified by
83 to locate the specified
85 program, instead of using the value of the
92 into multiple strings, and process each of the resulting strings
93 as separate arguments to the
98 option recognizes some special character escape sequences and
99 also supports environment-variable substitution, as described
103 If the environment variable
105 is in the environment, then remove it before processing the
107 This is similar to the
118 Print verbose information for each step of processing done by the
121 Additional information will be printed if
123 is specified multiple times.
126 The above options are only recognized when they are specified
128 .Ar name Ns = Ns Ar value
135 prints out the names and values of the variables in the environment.
136 Each name/value pair is separated by a new line unless
138 is specified, in which case name/value pairs are separated by NUL.
143 may not be specified together.
145 .Ss Details of Fl S \&Ss (split-string) processing
146 The processing of the
148 option will split the given
150 into separate arguments based on any space or <tab> characters found in the
152 Each of those new arguments will then be treated as if it had been
153 specified as a separate argument on the original
157 Spaces and tabs may be embedded in one of those new arguments by using
162 quotes, or backslashes
164 Single quotes will escape all non-single quote characters, up to
165 the matching single quote.
166 Double quotes will escape all non-double quote characters, up to
167 the matching double quote.
168 It is an error if the end of the
170 is reached before the matching quote character.
174 would create a new argument that starts with the
176 character, then that argument and the remainder of the
181 sequence can be used when you want a new argument to start
184 character, without causing the remainder of the
192 processing will treat certain character combinations as escape
193 sequences which represent some action to take.
194 The character escape sequences are in backslash notation.
195 The characters and their meanings are as follows:
197 .Bl -tag -width indent -offset indent -compact
199 Ignore the remaining characters in the
201 This must not appear inside a double-quoted string.
203 Replace with a <form-feed> character.
205 Replace with a <new-line> character.
207 Replace with a <carriage return> character.
209 Replace with a <tab> character.
211 Replace with a <vertical tab> character.
216 This would be useful when you need a
218 as the first character in one of the arguments created
219 by splitting apart the given
226 If this is found inside of a double-quoted string, then replace it
228 If this is found outside of a quoted string, then treat this as the
229 separator character between new arguments in the original
232 Replace with a <double quote> character.
234 Replace with a <single quote> character.
236 Replace with a backslash character.
239 The sequences for <single-quote> and backslash are the only sequences
240 which are recognized inside of a single-quoted string.
241 The other sequences have no special meaning inside a single-quoted
243 All escape sequences are recognized inside of a double-quoted string.
244 It is an error if a single
246 character is followed by a character other than the ones listed above.
250 also supports substitution of values from environment variables.
251 To do this, the name of the environment variable must be inside of
255 The common shell syntax of
258 All values substituted will be the values of the environment variables
259 as they were when the
261 utility was originally invoked.
262 Those values will not be checked for any of the escape sequences as
265 .Ar name Ns = Ns Ar value
266 will not effect the values used for substitution in
272 processing can not reference the value of the special parameters
273 which are defined by most shells.
276 can not recognize special parameters such as:
283 if they appear inside the given
286 .Ss Use in shell-scripts
289 utility is often used as the
291 on the first line of interpreted scripts, as
295 Note that the way the kernel parses the
297 (first line) of an interpreted script has changed as of
301 kernel would split that first line into separate arguments based
302 on any whitespace (space or <tab> characters) found in the line.
303 So, if a script named
304 .Pa /usr/local/bin/someport
307 .Dl "#!/usr/local/bin/php -n -q -dsafe_mode=0"
310 .Pa /usr/local/bin/php
311 program would have been started with the arguments of:
312 .Bd -literal -offset indent
313 arg[0] = '/usr/local/bin/php'
316 arg[3] = '-dsafe_mode=0'
317 arg[4] = '/usr/local/bin/someport'
320 plus any arguments the user specified when executing
322 However, this processing of multiple options on the
324 line is not the way any other operating system parses the
325 first line of an interpreted script.
326 So after a change which was made for
328 release, that script will result in
329 .Pa /usr/local/bin/php
330 being started with the arguments of:
331 .Bd -literal -offset indent
332 arg[0] = '/usr/local/bin/php'
333 arg[1] = '-n -q -dsafe_mode=0'
334 arg[2] = '/usr/local/bin/someport'
337 plus any arguments the user specified.
338 This caused a significant change in the behavior of a few scripts.
339 In the case of above script, to have it behave the same way under
341 as it did under earlier releases, the first line should be
344 .Dl "#!/usr/bin/env -S /usr/local/bin/php -n -q -dsafe_mode=0"
348 utility will be started with the entire line as a single
351 .Dl "arg[1] = '-S /usr/local/bin/php -n -q -dsafe_mode=0'"
355 processing will split that line into separate arguments before
357 .Pa /usr/local/bin/php .
364 environment variable to locate the requested
366 if the name contains no
368 characters, unless the
370 option has been specified.
373 An exit status of 126 indicates that
375 was found, but could not be executed.
376 An exit status of 127 indicates that
382 utility is often used as part of the first line of an interpreted script,
383 the following examples show a number of ways that the
385 utility can be useful in scripts.
387 The kernel processing of an interpreted script does not allow a script
388 to directly reference some other script as its own interpreter.
389 As a way around this, the main difference between
391 .Dl #!/usr/local/bin/foo
393 .Dl "#!/usr/bin/env /usr/local/bin/foo"
395 is that the latter works even if
396 .Pa /usr/local/bin/foo
397 is itself an interpreted script.
399 Probably the most common use of
401 is to find the correct interpreter for a script, when the interpreter
402 may be in different directories on different systems.
403 The following example will find the
405 interpreter by searching through the directories specified by
408 .Dl "#!/usr/bin/env perl"
410 One limitation of that example is that it assumes the user's value
413 is set to a value which will find the interpreter you want
417 option can be used to make sure a specific list of directories is
418 used in the search for
422 option is also required for this example to work correctly.
424 .Dl "#!/usr/bin/env -S -P/usr/local/bin:/usr/bin perl"
432 That could be combined with the present value of
434 to provide more flexibility.
435 Note that spaces are not required between the
441 .Dl "#!/usr/bin/env -S-P/usr/local/bin:/usr/bin:${PATH} perl"
447 option as a synonym for
463 options are non-standard extensions supported by
465 but which may not be available on other operating systems.
475 options were added in
480 utility does not handle values of
482 which have an equals sign
484 in their name, for obvious reasons.
488 utility does not take multibyte characters into account when
491 option, which may lead to incorrect results in some locales.