1TEST(1P) POSIX Programmer's Manual TEST(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 test — evaluate expression
13
15 test [expression]
16 [ [expression] ]
18
20 The test utility shall evaluate the expression and indicate the result
21 of the evaluation by its exit status. An exit status of zero indicates
22 that the expression evaluated as true and an exit status of 1 indicates
23 that the expression evaluated as false.
24 In the second form of the utility, where the utility name used is [
26 rather than test, the application shall ensure that the closing square
27 bracket is a separate argument. The test and [ utilities may be imple‐
28 mented as a single linked utility which examines the basename of the
29 zeroth command line argument to determine whether to behave as the test
30 or [ variant. Applications using the exec() family of functions to exe‐
31 cute these utilities shall ensure that the argument passed in arg0 or
32 argv[0] is '[' when executing the [ utility and has a basename of
33 "test" when executing the test utility.
34
36 The test utility shall not recognize the "--" argument in the manner
37 specified by Guideline 10 in the Base Definitions volume of
38 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
39 No options shall be supported.
41
43 The application shall ensure that all operators and elements of pri‐
44 maries are presented as separate arguments to the test utility.
45 The following primaries can be used to construct expression:
47 -b pathname
49 True if pathname resolves to an existing directory entry for
50 a block special file. False if pathname cannot be resolved,
51 or if pathname resolves to an existing directory entry for a
52 file that is not a block special file.
53 -c pathname
55 True if pathname resolves to an existing directory entry for
56 a character special file. False if pathname cannot be
57 resolved, or if pathname resolves to an existing directory
58 entry for a file that is not a character special file.
59 -d pathname
61 True if pathname resolves to an existing directory entry for
62 a directory. False if pathname cannot be resolved, or if
63 pathname resolves to an existing directory entry for a file
64 that is not a directory.
65 -e pathname
67 True if pathname resolves to an existing directory entry.
68 False if pathname cannot be resolved.
69 -f pathname
71 True if pathname resolves to an existing directory entry for
72 a regular file. False if pathname cannot be resolved, or if
73 pathname resolves to an existing directory entry for a file
74 that is not a regular file.
75 -g pathname
77 True if pathname resolves to an existing directory entry for
78 a file that has its set-group-ID flag set. False if pathname
79 cannot be resolved, or if pathname resolves to an existing
80 directory entry for a file that does not have its set-group-
81 ID flag set.
82 -h pathname
84 True if pathname resolves to an existing directory entry for
85 a symbolic link. False if pathname cannot be resolved, or if
86 pathname resolves to an existing directory entry for a file
87 that is not a symbolic link. If the final component of path‐
88 name is a symbolic link, that symbolic link is not followed.
89 -L pathname
91 True if pathname resolves to an existing directory entry for
92 a symbolic link. False if pathname cannot be resolved, or if
93 pathname resolves to an existing directory entry for a file
94 that is not a symbolic link. If the final component of path‐
95 name is a symbolic link, that symbolic link is not followed.
96 -n string True if the length of string is non-zero; otherwise, false.
98 -p pathname
100 True if pathname resolves to an existing directory entry for
101 a FIFO. False if pathname cannot be resolved, or if pathname
102 resolves to an existing directory entry for a file that is
103 not a FIFO.
104 -r pathname
106 True if pathname resolves to an existing directory entry for
107 a file for which permission to read from the file will be
108 granted, as defined in Section 1.1.1.4, File Read, Write, and
109 Creation. False if pathname cannot be resolved, or if path‐
110 name resolves to an existing directory entry for a file for
111 which permission to read from the file will not be granted.
112 -S pathname
114 True if pathname resolves to an existing directory entry for
115 a socket. False if pathname cannot be resolved, or if path‐
116 name resolves to an existing directory entry for a file that
117 is not a socket.
118 -s pathname
120 True if pathname resolves to an existing directory entry for
121 a file that has a size greater than zero. False if pathname
122 cannot be resolved, or if pathname resolves to an existing
123 directory entry for a file that does not have a size greater
124 than zero.
125 -t file_descriptor
127 True if file descriptor number file_descriptor is open and is
128 associated with a terminal. False if file_descriptor is not a
129 valid file descriptor number, or if file descriptor number
130 file_descriptor is not open, or if it is open but is not
131 associated with a terminal.
132 -u pathname
134 True if pathname resolves to an existing directory entry for
135 a file that has its set-user-ID flag set. False if pathname
136 cannot be resolved, or if pathname resolves to an existing
137 directory entry for a file that does not have its set-user-ID
138 flag set.
139 -w pathname
141 True if pathname resolves to an existing directory entry for
142 a file for which permission to write to the file will be
143 granted, as defined in Section 1.1.1.4, File Read, Write, and
144 Creation. False if pathname cannot be resolved, or if path‐
145 name resolves to an existing directory entry for a file for
146 which permission to write to the file will not be granted.
147 -x pathname
149 True if pathname resolves to an existing directory entry for
150 a file for which permission to execute the file (or search
151 it, if it is a directory) will be granted, as defined in Sec‐
152 tion 1.1.1.4, File Read, Write, and Creation. False if path‐
153 name cannot be resolved, or if pathname resolves to an exist‐
154 ing directory entry for a file for which permission to exe‐
155 cute (or search) the file will not be granted.
156 -z string True if the length of string string is zero; otherwise,
158 false.
159 string True if the string string is not the null string; otherwise,
161 false.
162 s1 = s2 True if the strings s1 and s2 are identical; otherwise,
164 false.
165 s1 != s2 True if the strings s1 and s2 are not identical; otherwise,
167 false.
168 n1 -eq n2 True if the integers n1 and n2 are algebraically equal; oth‐
170 erwise, false.
171 n1 -ne n2 True if the integers n1 and n2 are not algebraically equal;
173 otherwise, false.
174 n1 -gt n2 True if the integer n1 is algebraically greater than the
176 integer n2; otherwise, false.
177 n1 -ge n2 True if the integer n1 is algebraically greater than or equal
179 to the integer n2; otherwise, false.
180 n1 -lt n2 True if the integer n1 is algebraically less than the integer
182 n2; otherwise, false.
183 n1 -le n2 True if the integer n1 is algebraically less than or equal to
185 the integer n2; otherwise, false.
186 expression1 -a expression2
188 True if both expression1 and expression2 are true; otherwise,
189 false. The -a binary primary is left associative. It has a
190 higher precedence than -o.
191 expression1 -o expression2
193 True if either expression1 or expression2 is true; otherwise,
194 false. The -o binary primary is left associative.
195 With the exception of the -h pathname and -L pathname primaries, if a
197 pathname argument is a symbolic link, test shall evaluate the expres‐
198 sion by resolving the symbolic link and using the file referenced by
199 the link.
200 These primaries can be combined with the following operators:
202 ! expression
204 True if expression is false. False if expression is true.
205 ( expression )
207 True if expression is true. False if expression is false. The
208 parentheses can be used to alter the normal precedence and
209 associativity.
210 The primaries with two elements of the form:
212 -primary_operator primary_operand
215 are known as unary primaries. The primaries with three elements in
217 either of the two forms:
218 primary_operand -primary_operator primary_operand
221 primary_operand primary_operator primary_operand
223 are known as binary primaries. Additional implementation-defined oper‐
225 ators and primary_operators may be provided by implementations. They
226 shall be of the form -operator where the first character of operator is
227 not a digit.
228 The algorithm for determining the precedence of the operators and the
230 return value that shall be generated is based on the number of argu‐
231 ments presented to test. (However, when using the "[...]" form, the
232 <right-square-bracket> final argument shall not be counted in this
233 algorithm.)
234 In the following list, $1, $2, $3, and $4 represent the arguments pre‐
236 sented to test:
237 0 arguments:
239 Exit false (1).
240 1 argument: Exit true (0) if $1 is not null; otherwise, exit false.
242 2 arguments:
244 * If $1 is '!', exit true if $2 is null, false if $2 is
245 not null.
246 * If $1 is a unary primary, exit true if the unary test
248 is true, false if the unary test is false.
249 * Otherwise, produce unspecified results.
251 3 arguments:
253 * If $2 is a binary primary, perform the binary test of
254 $1 and $3.
255 * If $1 is '!', negate the two-argument test of $2 and
257 $3.
258 * If $1 is '(' and $3 is ')', perform the unary test of
260 $2. On systems that do not support the XSI option, the
261 results are unspecified if $1 is '(' and $3 is ')'.
262 * Otherwise, produce unspecified results.
264 4 arguments:
266 * If $1 is '!', negate the three-argument test of $2, $3,
267 and $4.
268 * If $1 is '(' and $4 is ')', perform the two-argument
270 test of $2 and $3. On systems that do not support the
271 XSI option, the results are unspecified if $1 is '('
272 and $4 is ')'.
273 * Otherwise, the results are unspecified.
275 >4 arguments:
277 The results are unspecified.
278 On XSI-conformant systems, combinations of primaries and
280 operators shall be evaluated using the precedence and asso‐
281 ciativity rules described previously. In addition, the
282 string comparison binary primaries '=' and "!=" shall have
283 a higher precedence than any unary primary.
284
286 Not used.
287
289 None.
290
292 The following environment variables shall affect the execution of test:
293 LANG Provide a default value for the internationalization vari‐
295 ables that are unset or null. (See the Base Definitions vol‐
296 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
297 ables for the precedence of internationalization variables
298 used to determine the values of locale categories.)
299 LC_ALL If set to a non-empty string value, override the values of
301 all the other internationalization variables.
302 LC_CTYPE Determine the locale for the interpretation of sequences of
304 bytes of text data as characters (for example, single-byte as
305 opposed to multi-byte characters in arguments).
306 LC_MESSAGES
308 Determine the locale that should be used to affect the format
309 and contents of diagnostic messages written to standard
310 error.
311 NLSPATH Determine the location of message catalogs for the processing
313 of LC_MESSAGES.
314
316 Default.
317
319 Not used.
320
322 The standard error shall be used only for diagnostic messages.
323
325 None.
326
328 None.
329
331 The following exit values shall be returned:
332 0 expression evaluated to true.
334 1 expression evaluated to false or expression was missing.
336 >1 An error occurred.
338
340 Default.
341 The following sections are informative.
343
345 The XSI extensions specifying the -a and -o binary primaries and the
346 '(' and ')' operators have been marked obsolescent. (Many expressions
347 using them are ambiguously defined by the grammar depending on the spe‐
348 cific expressions being evaluated.) Scripts using these expressions
349 should be converted to the forms given below. Even though many imple‐
350 mentations will continue to support these obsolescent forms, scripts
351 should be extremely careful when dealing with user-supplied input that
352 could be confused with these and other primaries and operators. Unless
353 the application developer knows all the cases that produce input to the
354 script, invocations like:
355 test "$1" -a "$2"
358 should be written as:
360 test "$1" && test "$2"
363 to avoid problems if a user supplied values such as $1 set to '!' and
365 $2 set to the null string. That is, in cases where maximal portability
366 is of concern, replace:
367 test expr1 -a expr2
370 with:
372 test expr1 && test expr2
375 and replace:
377 test expr1 -o expr2
380 with:
382 test expr1 || test expr2
385 but note that, in test, -a has higher precedence than -o while "&&" and
387 "||" have equal precedence in the shell.
388 Parentheses or braces can be used in the shell command language to
390 effect grouping.
391 Parentheses must be escaped when using sh; for example:
393 test \( expr1 -a expr2 \) -o expr3
396 This command is not always portable even on XSI-conformant systems
398 depending on the expressions specified by expr1, expr2, and expr3. The
399 following form can be used instead:
400 ( test expr1 && test expr2 ) || test expr3
403 The two commands:
405 test "$1"
408 test ! "$1"
409 could not be used reliably on some historical systems. Unexpected
411 results would occur if such a string expression were used and $1
412 expanded to '!', '(', or a known unary primary. Better constructs are:
413 test -n "$1"
416 test -z "$1"
417 respectively.
419 Historical systems have also been unreliable given the common con‐
421 struct:
422 test "$response" = "expected string"
425 One of the following is a more reliable form:
427 test "X$response" = "Xexpected string"
430 test "expected string" = "$response"
431 Note that the second form assumes that expected string could not be
433 confused with any unary primary. If expected string starts with '-',
434 '(', '!', or even '=', the first form should be used instead. Using the
435 preceding rules without the XSI marked extensions, any of the three
436 comparison forms is reliable, given any input. (However, note that the
437 strings are quoted in all cases.)
438 Because the string comparison binary primaries, '=' and "!=", have a
440 higher precedence than any unary primary in the greater than 4 argument
441 case, unexpected results can occur if arguments are not properly pre‐
442 pared. For example, in:
443 test -d $1 -o -d $2
446 If $1 evaluates to a possible directory name of '=', the first three
448 arguments are considered a string comparison, which shall cause a syn‐
449 tax error when the second -d is encountered. One of the following forms
450 prevents this; the second is preferred:
451 test \( -d "$1" \) -o \( -d "$2" \)
454 test -d "$1" || test -d "$2"
455 Also in the greater than 4 argument case:
457 test "$1" = "bat" -a "$2" = "ball"
460 syntax errors occur if $1 evaluates to '(' or '!'. One of the follow‐
462 ing forms prevents this; the third is preferred:
463 test "X$1" = "Xbat" -a "X$2" = "Xball"
466 test "$1" = "bat" && test "$2" = "ball"
467 test "X$1" = "Xbat" && test "X$2" = "Xball"
468 Note that none of the following examples are permitted by the syntax
470 described:
471 [-f file]
474 [-f file ]
475 [ -f file]
476 [ -f file
477 test -f file ]
478 In the first two cases, if a utility named [‐f exists, that utility
480 would be invoked, and not test. In the remaining cases, the brackets
481 are mismatched, and the behavior is unspecified. However:
482 test ! ]
485 does have a defined meaning, and must exit with status 1. Similarly:
487 test ]
490 must exit with status 0.
492
494 1. Exit if there are not two or three arguments (two variations):
495 if [ $# -ne 2 ] && [ $# -ne 3 ]; then exit 1; fi
498 if [ $# -lt 2 ] || [ $# -gt 3 ]; then exit 1; fi
499 2. Perform a mkdir if a directory does not exist:
501 test ! -d tempdir && mkdir tempdir
504 3. Wait for a file to become non-readable:
506 while test -r thefile
509 do
510 sleep 30
511 done
512 echo '"thefile" is no longer readable'
513 4. Perform a command if the argument is one of three strings (two
515 variations):
516 if [ "$1" = "pear" ] || [ "$1" = "grape" ] || [ "$1" = "apple" ]
519 then
520 command
521 fi
522 case "$1" in
524 pear|grape|apple) command ;;
525 esac
526
528 The KornShell-derived conditional command (double bracket [[]]) was
529 removed from the shell command language description in an early pro‐
530 posal. Objections were raised that the real problem is misuse of the
531 test command ([), and putting it into the shell is the wrong way to fix
532 the problem. Instead, proper documentation and a new shell reserved
533 word (!) are sufficient.
534 Tests that require multiple test operations can be done at the shell
536 level using individual invocations of the test command and shell logi‐
537 cals, rather than using the error-prone -o flag of test.
538 XSI-conformant systems support more than four arguments.
540 XSI-conformant systems support the combining of primaries with the fol‐
542 lowing constructs:
543 expression1 -a expression2
545 True if both expression1 and expression2 are true.
546 expression1 -o expression2
548 True if at least one of expression1 and expression2 are true.
549 ( expression )
551 True if expression is true.
552 In evaluating these more complex combined expressions, the following
554 precedence rules are used:
555 * The unary primaries have higher precedence than the algebraic
557 binary primaries.
558 * The unary primaries have lower precedence than the string binary
560 primaries.
561 * The unary and binary primaries have higher precedence than the
563 unary string primary.
564 * The ! operator has higher precedence than the -a operator, and the
566 -a operator has higher precedence than the -o operator.
567 * The -a and -o operators are left associative.
569 * The parentheses can be used to alter the normal precedence and
571 associativity.
572 The BSD and System V versions of -f are not the same. The BSD defini‐
574 tion was:
575 -f file True if file exists and is not a directory.
577 The SVID version (true if the file exists and is a regular file) was
579 chosen for this volume of POSIX.1‐2017 because its use is consistent
580 with the -b, -c, -d, and -p operands (file exists and is a specific
581 file type).
582 The -e primary, possessing similar functionality to that provided by
584 the C shell, was added because it provides the only way for a shell
585 script to find out if a file exists without trying to open the file.
586 Since implementations are allowed to add additional file types, a por‐
587 table script cannot use:
588 test -b foo -o -c foo -o -d foo -o -f foo -o -p foo
591 to find out if foo is an existing file. On historical BSD systems, the
593 existence of a file could be determined by:
594 test -f foo -o -d foo
597 but there was no easy way to determine that an existing file was a reg‐
599 ular file. An early proposal used the KornShell -a primary (with the
600 same meaning), but this was changed to -e because there were concerns
601 about the high probability of humans confusing the -a primary with the
602 -a binary operator.
603 The following options were not included in this volume of POSIX.1‐2017,
605 although they are provided by some implementations. These operands
606 should not be used by new implementations for other purposes:
607 -k file True if file exists and its sticky bit is set.
609 -C file True if file is a contiguous file.
611 -V file True if file is a version file.
613 The following option was not included because it was undocumented in
615 most implementations, has been removed from some implementations
616 (including System V), and the functionality is provided by the shell
617 (see Section 2.6.2, Parameter Expansion.
618 -l string The length of the string string.
620 The -b, -c, -g, -p, -u, and -x operands are derived from the SVID; his‐
622 torical BSD does not provide them. The -k operand is derived from Sys‐
623 tem V; historical BSD does not provide it.
624 On historical BSD systems, test -w directory always returned false
626 because test tried to open the directory for writing, which always
627 fails.
628 Some additional primaries newly invented or from the KornShell appeared
630 in an early proposal as part of the conditional command ([[]]): s1 >
631 s2, s1 < s2, str = pattern, str != pattern, f1 -nt f2, f1 -ot f2, and
632 f1 -ef f2. They were not carried forward into the test utility when
633 the conditional command was removed from the shell because they have
634 not been included in the test utility built into historical implementa‐
635 tions of the sh utility.
636 The -t file_descriptor primary is shown with a mandatory argument
638 because the grammar is ambiguous if it can be omitted. Historical
639 implementations have allowed it to be omitted, providing a default of
640 1.
641 It is noted that '[' is not part of the portable filename character
643 set; however, since it is required to be encoded by a single byte, and
644 is part of the portable character set, the name of this utility forms a
645 character string across all supported locales.
646
648 None.
649
651 Section 1.1.1.4, File Read, Write, and Creation, find
652 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
654 Variables, Section 12.2, Utility Syntax Guidelines
655
657 Portions of this text are reprinted and reproduced in electronic form
658 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
659 table Operating System Interface (POSIX), The Open Group Base Specifi‐
660 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
661 Electrical and Electronics Engineers, Inc and The Open Group. In the
662 event of any discrepancy between this version and the original IEEE and
663 The Open Group Standard, the original IEEE and The Open Group Standard
664 is the referee document. The original Standard can be obtained online
665 at http://www.opengroup.org/unix/online.html .
666 Any typographical or formatting errors that appear in this page are
668 most likely to have been introduced during the conversion of the source
669 files to man page format. To report such errors, see https://www.ker‐
670 nel.org/doc/man-pages/reporting_bugs.html .
671IEEE/The Open Group 2017 TEST(1P)