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34 .\" From @(#)printenv.1 8.1 (Berkeley) 6/6/93
35 .\" From FreeBSD: src/usr.bin/printenv/printenv.1,v 1.17 2002/11/26 17:33:35 ru Exp
43 .Nd set environment and execute command, or print environment
49 .Op Ar name Ns = Ns Ar value ...
50 .Op Ar utility Op Ar argument ...
54 utility executes another
56 after modifying the environment as
57 specified on the command line.
59 .Ar name Ns = Ns Ar value
60 option specifies the setting of an environment variable,
64 All such environment variables are set before the
68 The options are as follows:
69 .Bl -tag -width indent
73 with only those environment variables specified by
74 .Ar name Ns = Ns Ar value
76 The environment inherited
79 is ignored completely.
82 Search the set of directories as specified by
84 to locate the specified
86 program, instead of using the value of the
93 into multiple strings, and process each of the resulting strings
94 as separate arguments to the
99 option recognizes some special character escape sequences and
100 also supports environment-variable substitution, as described
104 Print verbose information for each step of processing done by the
107 Additional information will be printed if
109 is specified multiple times.
112 The above options are only recognized when they are specified
114 .Ar name Ns = Ns Ar value
121 prints out the names and values
122 of the variables in the environment, with one name/value pair per line.
124 .Ss Details of Fl S Ss (split-string) processing
125 The processing of the
127 option will split the given
129 into separate arguments based on any space or <tab> characters found in the
131 Each of those new arguments will then be treated as if it had been
132 specified as a separate argument on the original
136 Spaces and tabs may be embedded in one of those new arguments by using
141 quotes, or backslashes
143 Single quotes will escape all non-single quote characters, up to
144 the matching single quote.
145 Double quotes will escape all non-double quote characters, up to
146 the matching double quote.
147 It is an error if the end of the
149 is reached before the matching quote character.
153 would create a new argument that starts with the
155 character, then that argument and the remainder of the
160 sequence can be used when you want a new argument to start
163 character, without causing the remainder of the
171 processing will treat certain character combinations as escape
172 sequences which represent some action to take.
173 The character escape sequences are in backslash notation.
174 The characters and their meanings are as follows:
176 .Bl -tag -width indent -offset indent -compact
178 Ignore the remaining characters in the
180 This must not appear inside a double-quoted string.
182 Replace with a <form-feed> character.
184 Replace with a <new-line> character.
186 Replace with a <carriage return> character.
188 Replace with a <tab> character.
190 Replace with a <vertical tab> character.
195 This would be useful when you need a
197 as the first character in one of the arguments created
198 by splitting apart the given
205 If this is found inside of a double-quoted string, then replace it
207 If this is found outside of a quoted string, then treat this as the
208 separator character between new arguments in the original
211 Replace with a <double quote> character.
213 Replace with a <single quote> character.
215 Replace with a backslash character.
218 The sequences for <single-quote> and backslash are the only sequences
219 which are recognized inside of a single-quoted string.
220 The other sequences have no special meaning inside a single-quoted
222 All escape sequences are recognized inside of a double-quoted string.
223 It is an error if a single
225 character is followed by a character other than the ones listed above.
229 also supports substitution of values from environment variables.
230 To do this, the name of the environment variable must be inside of
234 The common shell syntax of
237 All values substituted will be the values of the environment variables
238 as they were when the
240 utility was originally invoked.
241 Those values will not be checked for any of the escape sequences as
244 .Ar name Ns = Ns Ar value
245 will not effect the values used for substitution in
251 processing can not reference the value of the special parameters
252 which are defined by most shells.
255 can not recognize special parameters such as:
262 if they appear inside the given
265 .Ss Use in shell-scripts
268 utility is often used as the
270 on the first line of interpreted scripts, as
274 Note that the way the kernel parses the
276 (first line) of an interpreted script has changed as of
280 kernel would split that first line into separate arguments based
281 on any whitespace (space or <tab> characters) found in the line.
282 So, if a script named
283 .Pa /usr/local/bin/someport
286 .Dl "#!/usr/local/bin/php -n -q -dsafe_mode=0"
289 .Pa /usr/local/bin/php
290 program would have been started with the arguments of:
291 .Bd -literal -offset indent
292 arg[0] = '/usr/local/bin/php'
295 arg[3] = '-dsafe_mode=0'
296 arg[4] = '/usr/local/bin/someport'
299 plus any arguments the user specified when executing
301 However, this processing of multiple options on the
303 line is not the way any other operating system parses the
304 first line of an interpreted script.
305 So after a change which was made for
307 release, that script will result in
308 .Pa /usr/local/bin/php
309 being started with the arguments of:
310 .Bd -literal -offset indent
311 arg[0] = '/usr/local/bin/php'
312 arg[1] = '-n -q -dsafe_mode=0'
313 arg[2] = '/usr/local/bin/someport'
316 plus any arguments the user specified.
317 This caused a significant change in the behavior of a few scripts.
318 In the case of above script, to have it behave the same way under
320 as it did under earlier releases, the first line should be
323 .Dl "#!/usr/bin/env -S /usr/local/bin/php -n -q -dsafe_mode=0"
327 utility will be started with the entire line as a single
330 .Dl "arg[1] = '-S /usr/local/bin/php -n -q -dsafe_mode=0'"
334 processing will split that line into separate arguments before
336 .Pa /usr/local/bin/php .
343 environment variable to locate the requested
345 if the name contains no
347 characters, unless the
349 option has been specified.
352 An exit status of 126 indicates that
354 was found, but could not be executed.
355 An exit status of 127 indicates that
361 utility is often used as part of the first line of an interpreted script,
362 the following examples show a number of ways that the
364 utility can be useful in scripts.
366 The kernel processing of an interpreted script does not allow a script
367 to directly reference some other script as its own interpreter.
368 As a way around this, the main difference between
370 .Dl #!/usr/local/bin/foo
372 .Dl "#!/usr/bin/env /usr/local/bin/foo"
374 is that the latter works even if
375 .Pa /usr/local/bin/foo
376 is itself an interpreted script.
378 Probably the most common use of
380 is to find the correct interpreter for a script, when the interpreter
381 may be in different directories on different systems.
382 The following example will find the
384 interpreter by searching through the directories specified by
387 .Dl "#!/usr/bin/env perl"
389 One limitation of that example is that it assumes the user's value
392 is set to a value which will find the interpreter you want
396 option can be used to make sure a specific list of directories is
397 used in the search for
401 option is also required for this example to work correctly.
403 .Dl "#!/usr/bin/env -S -P/usr/local/bin:/usr/bin perl"
411 That could be combined with the present value of
413 to provide more flexibility.
414 Note that spaces are not required between the
420 .Dl "#!/usr/bin/env -S-P/usr/local/bin:/usr/bin:${PATH} perl"
426 option as a synonym for
442 options are non-standard
444 extensions which may not be available on other operating systems.
454 options were added in
459 utility does not handle values of
461 which have an equals sign
463 in their name, for obvious reasons.
467 utility does not take multibyte characters into account when
470 option, which may lead to incorrect results in some locales.