man-pages/man1p/test.1p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "TEST" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" test 
.SH NAME
test \- evaluate expression
.SH SYNOPSIS
.LP
\fBtest\fP \fB[\fP\fIexpression\fP\fB]\fP\fB
.br
.sp
[\fP \fB[\fP\fIexpression\fP\fB]\fP \fB]
.br
\fP
.SH DESCRIPTION
.LP
The \fItest\fP utility shall evaluate the \fIexpression\fP and indicate
the result of the evaluation by its exit status. An
exit status of zero indicates that the expression evaluated as true
and an exit status of 1 indicates that the expression evaluated
as false.
.LP
In the second form of the utility, which uses \fB"[]"\fP rather than
\fItest\fP, the application shall ensure that the
square brackets are separate arguments.
.SH OPTIONS
.LP
The \fItest\fP utility shall not recognize the \fB"--"\fP argument
in the manner specified by guideline 10 in the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility
Syntax
Guidelines.
.LP
No options shall be supported.
.SH OPERANDS
.LP
The application shall ensure that all operators and elements of primaries
are presented as separate arguments to the \fItest\fP
utility.
.LP
The following primaries can be used to construct \fIexpression\fP:
.TP 7
\fB-b\ \fP \fIfile\fP
True if \fIfile\fP exists and is a block special file.
.TP 7
\fB-c\ \fP \fIfile\fP
True if \fIfile\fP exists and is a character special file.
.TP 7
\fB-d\ \fP \fIfile\fP
True if \fIfile\fP exists and is a directory.
.TP 7
\fB-e\ \fP \fIfile\fP
True if \fIfile\fP exists.
.TP 7
\fB-f\ \fP \fIfile\fP
True if \fIfile\fP exists and is a regular file.
.TP 7
\fB-g\ \fP \fIfile\fP
True if \fIfile\fP exists and its set-group-ID flag is set.
.TP 7
\fB-h\ \fP \fIfile\fP
True if \fIfile\fP exists and is a symbolic link.
.TP 7
\fB-L\ \fP \fIfile\fP
True if \fIfile\fP exists and is a symbolic link.
.TP 7
\fB-n\ \fP \fIstring\fP
True if the length of \fIstring\fP is non-zero.
.TP 7
\fB-p\ \fP \fIfile\fP
True if \fIfile\fP is a FIFO.
.TP 7
\fB-r\ \fP \fIfile\fP
True if \fIfile\fP exists and is readable. True shall indicate that
permission to read from \fIfile\fP will be granted, as
defined in \fIFile Read, Write, and Creation\fP .
.TP 7
\fB-S\ \fP \fIfile\fP
True if \fIfile\fP exists and is a socket.
.TP 7
\fB-s\ \fP \fIfile\fP
True if \fIfile\fP exists and has a size greater than zero.
.TP 7
\fB-t\ \fP \fIfile_descriptor\fP
.sp
True if the file whose file descriptor number is \fIfile_descriptor\fP
is open and is associated with a terminal.
.TP 7
\fB-u\ \fP \fIfile\fP
True if \fIfile\fP exists and its set-user-ID flag is set.
.TP 7
\fB-w\ \fP \fIfile\fP
True if \fIfile\fP exists and is writable. True shall indicate that
permission to write from \fIfile\fP will be granted, as
defined in \fIFile Read, Write, and Creation\fP .
.TP 7
\fB-x\ \fP \fIfile\fP
True if \fIfile\fP exists and is executable. True shall indicate that
permission to execute \fIfile\fP will be granted, as
defined in \fIFile Read, Write, and Creation\fP . If \fIfile\fP is
a directory,
true shall indicate that permission to search \fIfile\fP will be granted.
.TP 7
\fB-z\ \fP \fIstring\fP
True if the length of string \fIstring\fP is zero.
.TP 7
\fIstring\fP
True if the string \fIstring\fP is not the null string.
.TP 7
\fIs1\fP\fB\ =\ \fP \fIs2\fP
True if the strings \fIs1\fP and \fIs2\fP are identical.
.TP 7
\fIs1\fP\fB\ !=\ \fP \fIs2\fP
True if the strings \fIs1\fP and \fIs2\fP are not identical.
.TP 7
\fIn1\fP\fB\ -eq\ \fP \fIn2\fP
True if the integers \fIn1\fP and \fIn2\fP are algebraically equal.
.TP 7
\fIn1\fP\fB\ -ne\ \fP \fIn2\fP
True if the integers \fIn1\fP and \fIn2\fP are not algebraically equal.
.TP 7
\fIn1\fP\fB\ -gt\ \fP \fIn2\fP
True if the integer \fIn1\fP is algebraically greater than the integer
\fIn2\fP.
.TP 7
\fIn1\fP\fB\ -ge\ \fP \fIn2\fP
True if the integer \fIn1\fP is algebraically greater than or equal
to the integer \fIn2\fP.
.TP 7
\fIn1\fP\fB\ -lt\ \fP \fIn2\fP
True if the integer \fIn1\fP is algebraically less than the integer
\fIn2\fP.
.TP 7
\fIn1\fP\fB\ -le\ \fP \fIn2\fP
True if the integer \fIn1\fP is algebraically less than or equal to
the integer \fIn2\fP.
.TP 7
\fIexpression1\fP\fB\ -a\ \fP \fIexpression2\fP
.sp
True if both \fIexpression1\fP and \fIexpression2\fP are true. The
\fB-a\fP binary primary is left associative. It has a higher
precedence than \fB-o\fP. 
.TP 7
\fIexpression1\fP\fB\ -o\ \fP \fIexpression2\fP
.sp
True if either \fIexpression1\fP or \fIexpression2\fP is true. The
\fB-o\fP binary primary is left associative. 
.sp
.LP
With the exception of the \fB-h\fP \fIfile\fP and \fB-L\fP \fIfile\fP
primaries, if a \fIfile\fP argument is a symbolic
link, \fItest\fP shall evaluate the expression by resolving the symbolic
link and using the file referenced by the link.
.LP
These primaries can be combined with the following operators:
.TP 7
\fB!\ \fP \fIexpression\fP
True if \fIexpression\fP is false.
.TP 7
\fB(\ \fP \fIexpression\ \fP \fB)\fP
True if \fIexpression\fP is true. The parentheses can be used to alter
the normal precedence and associativity. 
.sp
.LP
The primaries with two elements of the form:
.sp
.RS
.nf

\fB-\fP\fIprimary_operator primary_operand\fP
.fi
.RE
.LP
are known as \fIunary primaries\fP. The primaries with three elements
in either of the two forms:
.sp
.RS
.nf

\fIprimary_operand\fP \fB-\fP\fIprimary_operator primary_operand
.sp

primary_operand primary_operator primary_operand\fP
.fi
.RE
.LP
are known as \fIbinary primaries\fP. Additional implementation-defined
operators and \fIprimary_operator\fPs may be provided
by implementations. They shall be of the form - \fIoperator\fP where
the first character of \fIoperator\fP is not a digit.
.LP
The algorithm for determining the precedence of the operators and
the return value that shall be generated is based on the
number of arguments presented to \fItest\fP. (However, when using
the \fB"[...]"\fP form, the right-bracket final argument
shall not be counted in this algorithm.)
.LP
In the following list, $1, $2, $3, and $4 represent the arguments
presented to \fItest\fP:
.TP 7
0\ arguments:
Exit false (1).
.TP 7
1\ argument:
Exit true (0) if $1 is not null; otherwise, exit false.
.TP 7
2\ arguments:
.RS
.IP " *" 3
If $1 is \fB'!'\fP , exit true if $2 is null, false if $2 is not null.
.LP
.IP " *" 3
If $1 is a unary primary, exit true if the unary test is true, false
if the unary test is false.
.LP
.IP " *" 3
Otherwise, produce unspecified results.
.LP
.RE
.TP 7
3\ arguments:
.RS
.IP " *" 3
If $2 is a binary primary, perform the binary test of $1 and $3.
.LP
.IP " *" 3
If $1 is \fB'!'\fP , negate the two-argument test of $2 and $3.
.LP
.IP " *" 3
If $1 is \fB'('\fP and $3 is \fB')'\fP , perform the unary test of
$2. 
.LP
.IP " *" 3
Otherwise, produce unspecified results.
.LP
.RE
.TP 7
4\ arguments:
.RS
.IP " *" 3
If $1 is \fB'!'\fP , negate the three-argument test of $2, $3, and
$4.
.LP
.IP " *" 3
If $1 is \fB'('\fP and $4 is \fB')'\fP , perform the two-argument
test of $2 and $3. 
.LP
.IP " *" 3
Otherwise, the results are unspecified.
.LP
.RE
.TP 7
>4\ arguments:
The results are unspecified. 
.LP
On XSI-conformant systems, combinations of primaries and operators
shall be evaluated using the precedence and associativity rules
described previously. In addition, the string comparison binary primaries
\fB'='\fP and \fB"!="\fP shall have a higher
precedence than any unary primary. 
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fItest\fP:
.TP 7
\fILANG\fP
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
Not used.
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
\fIexpression\fP evaluated to true.
.TP 7
\ 1
\fIexpression\fP evaluated to false or \fIexpression\fP was missing.
.TP 7
>1
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
Scripts should be careful when dealing with user-supplied input that
could be confused with primaries and operators. Unless the
application writer knows all the cases that produce input to the script,
invocations like:
.sp
.RS
.nf

\fBtest "$1" -a "$2"
\fP
.fi
.RE
.LP
should be written as:
.sp
.RS
.nf

\fBtest "$1" && test "$2"
\fP
.fi
.RE
.LP
to avoid problems if a user supplied values such as $1 set to \fB'!'\fP
and $2 set to the null string. That is, in cases
where maximal portability is of concern, replace:
.sp
.RS
.nf

\fBtest expr1 -a expr2
\fP
.fi
.RE
.LP
with:
.sp
.RS
.nf

\fBtest expr1 && test expr2
\fP
.fi
.RE
.LP
and replace:
.sp
.RS
.nf

\fBtest expr1 -o expr2
\fP
.fi
.RE
.LP
with:
.sp
.RS
.nf

\fBtest expr1 || test expr2
\fP
.fi
.RE
.LP
but note that, in \fItest\fP, \fB-a\fP has higher precedence than
\fB-o\fP while \fB"&&"\fP and \fB"||"\fP have
equal precedence in the shell.
.LP
Parentheses or braces can be used in the shell command language to
effect grouping.
.LP
Parentheses must be escaped when using \fIsh\fP; for example:
.sp
.RS
.nf

\fBtest \\( expr1 -a expr2 \\) -o expr3
\fP
.fi
.RE
.LP
This command is not always portable outside XSI-conformant systems.
The following form can be used instead:
.sp
.RS
.nf

\fB( test expr1 && test expr2 ) || test expr3
\fP
.fi
.RE
.LP
The two commands:
.sp
.RS
.nf

\fBtest "$1"
test ! "$1"
\fP
.fi
.RE
.LP
could not be used reliably on some historical systems. Unexpected
results would occur if such a \fIstring\fP expression were
used and $1 expanded to \fB'!'\fP , \fB'('\fP , or a known unary primary.
Better constructs are:
.sp
.RS
.nf

\fBtest -n "$1"
test -z "$1"
\fP
.fi
.RE
respectively. 
.LP
Historical systems have also been unreliable given the common construct:
.sp
.RS
.nf

\fBtest "$response" = "expected string"
\fP
.fi
.RE
.LP
One of the following is a more reliable form:
.sp
.RS
.nf

\fBtest "X$response" = "Xexpected string"
test "expected string" = "$response"
\fP
.fi
.RE
.LP
Note that the second form assumes that \fIexpected string\fP could
not be confused with any unary primary. If \fIexpected
string\fP starts with \fB'-'\fP , \fB'('\fP , \fB'!'\fP , or even
\fB'='\fP , the first form should be used instead.
Using the preceding rules without the XSI marked extensions, any of
the three comparison forms is reliable, given any input.
(However, note that the strings are quoted in all cases.)
.LP
Because the string comparison binary primaries, \fB'='\fP and \fB"!="\fP
, have a higher precedence than any unary primary
in the greater than 4 argument case, unexpected results can occur
if arguments are not properly prepared. For example, in:
.sp
.RS
.nf

\fBtest -d $1 -o -d $2
\fP
.fi
.RE
.LP
If $1 evaluates to a possible directory name of \fB'='\fP , the first
three arguments are considered a string comparison,
which shall cause a syntax error when the second \fB-d\fP is encountered.
One of the following forms prevents this; the second is
preferred:
.sp
.RS
.nf

\fBtest \\( -d "$1" \\) -o \\( -d "$2" \\)
test -d "$1" || test -d "$2"
\fP
.fi
.RE
.LP
Also in the greater than 4 argument case:
.sp
.RS
.nf

\fBtest "$1" = "bat" -a "$2" = "ball"
\fP
.fi
.RE
.LP
syntax errors occur if $1 evaluates to \fB'('\fP or \fB'!'\fP . One
of the following forms prevents this; the third is
preferred:
.sp
.RS
.nf

\fBtest "X$1" = "Xbat" -a "X$2" = "Xball"
test "$1" = "bat" && test "$2" = "ball"
test "X$1" = "Xbat" && test "X$2" = "Xball"
\fP
.fi
.RE
.SH EXAMPLES
.IP " 1." 4
Exit if there are not two or three arguments (two variations):
.sp
.RS
.nf

\fBif [ $# -ne 2 -a $# -ne 3 ]; then exit 1; fi
if [ $# -lt 2 -o $# -gt 3 ]; then exit 1; fi
\fP
.fi
.RE
.LP
.IP " 2." 4
Perform a \fImkdir\fP if a directory does not exist:
.sp
.RS
.nf

\fBtest ! -d tempdir && mkdir tempdir
\fP
.fi
.RE
.LP
.IP " 3." 4
Wait for a file to become non-readable:
.sp
.RS
.nf

\fBwhile test -r thefile
do
    sleep 30
done
echo '"thefile" is no longer readable'
\fP
.fi
.RE
.LP
.IP " 4." 4
Perform a command if the argument is one of three strings (two variations):
.sp
.RS
.nf

\fBif [ "$1" = "pear" ] || [ "$1" = "grape" ] || [ "$1" = "apple" ]
then
   \fP \fIcommand\fP\fB
fi
.sp

case "$1" in
    pear|grape|apple)\fP \fIcommand\fP \fB;;
esac
\fP
.fi
.RE
.LP
.SH RATIONALE
.LP
The KornShell-derived conditional command (double bracket \fB[[]]\fP)
was removed from the shell command language description
in an early proposal. Objections were raised that the real problem
is misuse of the \fItest\fP command ( \fB[\fP), and putting it
into the shell is the wrong way to fix the problem. Instead, proper
documentation and a new shell reserved word ( \fB!\fP) are
sufficient.
.LP
Tests that require multiple \fItest\fP operations can be done at the
shell level using individual invocations of the
\fItest\fP command and shell logicals, rather than using the error-prone
\fB-o\fP flag of \fItest\fP.
.LP
XSI-conformant systems support more than four arguments.
.LP
XSI-conformant systems support the combining of primaries with the
following constructs:
.TP 7
\fIexpression1\fP \fB-a\fP \fIexpression2\fP
.sp
True if both \fIexpression1\fP and \fIexpression2\fP are true.
.TP 7
\fIexpression1\fP \fB-o\fP \fIexpression2\fP
.sp
True if at least one of \fIexpression1\fP and \fIexpression2\fP are
true.
.TP 7
\fB(\fP \fIexpression\fP \fB)\fP
.sp
True if \fIexpression\fP is true.
.sp
.LP
In evaluating these more complex combined expressions, the following
precedence rules are used:
.IP " *" 3
The unary primaries have higher precedence than the algebraic binary
primaries.
.LP
.IP " *" 3
The unary primaries have lower precedence than the string binary primaries.
.LP
.IP " *" 3
The unary and binary primaries have higher precedence than the unary
\fIstring\fP primary.
.LP
.IP " *" 3
The \fB!\fP operator has higher precedence than the \fB-a\fP operator,
and the \fB-a\fP operator has higher precedence than
the \fB-o\fP operator.
.LP
.IP " *" 3
The \fB-a\fP and \fB-o\fP operators are left associative.
.LP
.IP " *" 3
The parentheses can be used to alter the normal precedence and associativity.
.LP
.LP
The BSD and System V versions of \fB-f\fP are not the same. The BSD
definition was:
.TP 7
\fB-f\ \fP \fIfile\fP
True if \fIfile\fP exists and is not a directory.
.sp
.LP
The SVID version (true if the file exists and is a regular file) was
chosen for this volume of IEEE\ Std\ 1003.1-2001
because its use is consistent with the \fB-b\fP, \fB-c\fP, \fB-d\fP,
and \fB-p\fP operands ( \fIfile\fP exists and is a
specific file type).
.LP
The \fB-e\fP primary, possessing similar functionality to that provided
by the C shell, was added because it provides the only
way for a shell script to find out if a file exists without trying
to open the file. Since implementations are allowed to add
additional file types, a portable script cannot use:
.sp
.RS
.nf

\fBtest -b foo -o -c foo -o -d foo -o -f foo -o -p foo
\fP
.fi
.RE
.LP
to find out if \fBfoo\fP is an existing file. On historical BSD systems,
the existence of a file could be determined by:
.sp
.RS
.nf

\fBtest -f foo -o -d foo
\fP
.fi
.RE
.LP
but there was no easy way to determine that an existing file was a
regular file. An early proposal used the KornShell \fB-a\fP
primary (with the same meaning), but this was changed to \fB-e\fP
because there were concerns about the high probability of humans
confusing the \fB-a\fP primary with the \fB-a\fP binary operator.
.LP
The following options were not included in this volume of IEEE\ Std\ 1003.1-2001,
although they are provided by some
implementations. These operands should not be used by new implementations
for other purposes:
.TP 7
\fB-k\ \fP \fIfile\fP
True if \fIfile\fP exists and its sticky bit is set.
.TP 7
\fB-C\ \fP \fIfile\fP
True if \fIfile\fP is a contiguous file.
.TP 7
\fB-V\ \fP \fIfile\fP
True if \fIfile\fP is a version file.
.sp
.LP
The following option was not included because it was undocumented
in most implementations, has been removed from some
implementations (including System V), and the functionality is provided
by the shell (see \fIParameter Expansion\fP .
.TP 7
\fB-l\ \fP \fIstring\fP
The length of the string \fIstring\fP.
.sp
.LP
The \fB-b\fP, \fB-c\fP, \fB-g\fP, \fB-p\fP, \fB-u\fP, and \fB-x\fP
operands are derived from the SVID; historical BSD does
not provide them. The \fB-k\fP operand is derived from System V; historical
BSD does not provide it.
.LP
On historical BSD systems, \fItest\fP \fB-w\fP \fIdirectory\fP always
returned false because \fItest\fP tried to open the
directory for writing, which always fails.
.LP
Some additional primaries newly invented or from the KornShell appeared
in an early proposal as part of the conditional command
( \fB[[]]\fP): \fIs1\fP \fB>\fP \fIs2\fP, \fIs1\fP \fB<\fP \fIs2\fP,
\fIstr\fP \fB=\fP \fIpattern\fP, \fIstr\fP
\fB!=\fP \fIpattern\fP, \fIf1\fP \fB-nt\fP \fIf2\fP, \fIf1\fP \fB-ot\fP
\fIf2\fP, and \fIf1\fP \fB-ef\fP \fIf2\fP. They
were not carried forward into the \fItest\fP utility when the conditional
command was removed from the shell because they have not
been included in the \fItest\fP utility built into historical implementations
of the \fIsh\fP
utility.
.LP
The \fB-t\fP \fIfile_descriptor\fP primary is shown with a mandatory
argument because the grammar is ambiguous if it can be
omitted. Historical implementations have allowed it to be omitted,
providing a default of 1.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIFile Read, Write, and Creation\fP , \fIfind\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .