The shell keyword [[ requires a different syntax,
see below.
With bash:
Code:
$ type [[
[[ is a shell keyword
$ help [[
[[ ... ]]: [[ expression ]]
Returns a status of 0 or 1 depending on the evaluation of the conditional
expression EXPRESSION. Expressions are composed of the same primaries used
by the `test' builtin, and may be combined using the following operators
( EXPRESSION ) Returns the value of EXPRESSION
! EXPRESSION True if EXPRESSION is false; else false
EXPR1 && EXPR2 True if both EXPR1 and EXPR2 are true; else false
EXPR1 || EXPR2 True if either EXPR1 or EXPR2 is true; else false
When the `==' and `!=' operators are used, the string to the right of the
operator is used as a pattern and pattern matching is performed. The
&& and || operators do not evaluate EXPR2 if EXPR1 is sufficient to
determine the expression's value.
So:
Code:
$ [ x = x -a x = x ] && echo ok
ok
$ [[ x = x -a x = x ]] && echo ok
bash: syntax error in conditional expression
bash: syntax error near `-a'
I'm new to scripting and I need help with a bourn shell script. What i'm trying to do is a test condition where "if the time is within 2 hours, it's true" and so on.
The time is in the following format
DATE=`/bin/date +"%Y%m%d%H%S"`
for example, 20060907152000.
So, what the script first... (9 Replies)
Guys look at this:
i have to write a script that takes a file as an argument. The script should be able to determine what permissions the owner, group and everybody has for the file passed in. The output should be displayed similar to this.
READ WRITE EXECUTE
OWNER LEE.BALLANCORE YES YES NO... (9 Replies)
Hi ,
I have a doubt on condition test ( ] ). Pls refer blow program.
#!/bin/ksh
TEMP=
if ;then
echo $TEMP
else
print 'invalid option'
fi
Above script's TEMP variable has no value so it gives "invalid option" as output. But I got an error before priting the string .
Result :
... (2 Replies)
Hi there,
When I try to do a condition on test:
$ str1=abcd
$ test $str1
$ echo $?
0
Is there anyway to display the answer to be 'TRUE' or 'YES'? rather than 0?
If so, how can I do it without using awk or sed. (2 Replies)
Hello,
what is the better and correct way to perform a comparison:
I have been using the following with no problems:
if ]
then ....
fi
I have seen this also used :
if
then ....
fi
When I try :
if
then ....
fi
I get an error like .... the test condition expects a... (4 Replies)
I have a much larger script that takes an input file of hosts and determines if we support them and checks to ensure the FQDN coincides with our DNS. For instance, the hostname may return a different FQDN when passed to the "host" command, so I keep the value of the output of the "host" command... (4 Replies)
I want to locate directories that are upper, lower or have both upper and lower cases.
What I have is:
find /tmp/$var2 -type d' " ); && echo "host case is incorrect" || echo "host case is correct"
This actually is part of a larger script and it does work but the problem is that it... (3 Replies)
Without grep, I'd like to make a test condition so that any a word that does not have the successive letters car in it will be echoed. for example, bluecar will contain "car" so it will show up as a no
var=bluecar
$ echo $var|if ]; then echo "yes";fi
yes
this variable contains "car" so I... (5 Replies)
i have to test a condition for n times and if its value is greater than one each time for continuous 5 iterations it will take action
My Approach
run the same command 5 times in for loop and divert the output to a file and then read the values from file and use if else if and take action
... (1 Reply)
Discussion started by: abhaydas
1 Replies
LEARN ABOUT OSX
test
TEST(1) BSD General Commands Manual TEST(1)NAME
test, [ -- condition evaluation utility
SYNOPSIS
test expression
[ expression ]
DESCRIPTION
The test utility evaluates the expression and, if it evaluates to true, returns a zero (true) exit status; otherwise it returns 1 (false).
If there is no expression, test also returns 1 (false).
All operators and flags are separate arguments to the test utility.
The following primaries are used to construct expressions:
-b file True if file exists and is a block special file.
-c file True if file exists and is a character special file.
-d file True if file exists and is a directory.
-e file True if file exists (regardless of type).
-f file True if file exists and is a regular file.
-g file True if file exists and its set group ID flag is set.
-h file True if file exists and is a symbolic link. This operator is retained for compatibility with previous versions of this pro-
gram. Do not rely on its existence; use -L instead.
-k file True if file exists and its sticky bit is set.
-n string True if the length of string is nonzero.
-p file True if file is a named pipe (FIFO).
-r file True if file exists and is readable.
-s file True if file exists and has a size greater than zero.
-t file_descriptor
True if the file whose file descriptor number is file_descriptor is open and is associated with a terminal.
-u file True if file exists and its set user ID flag is set.
-w file True if file exists and is writable. True indicates only that the write flag is on. The file is not writable on a read-only
file system even if this test indicates true.
-x file True if file exists and is executable. True indicates only that the execute flag is on. If file is a directory, true indi-
cates that file can be searched.
-z string True if the length of string is zero.
-L file True if file exists and is a symbolic link.
-O file True if file exists and its owner matches the effective user id of this process.
-G file True if file exists and its group matches the effective group id of this process.
-S file True if file exists and is a socket.
file1 -nt file2
True if file1 exists and is newer than file2.
file1 -ot file2
True if file1 exists and is older than file2.
file1 -ef file2
True if file1 and file2 exist and refer to the same file.
string True if string is not the null string.
s1 = s2 True if the strings s1 and s2 are identical.
s1 != s2 True if the strings s1 and s2 are not identical.
s1 < s2 True if string s1 comes before s2 based on the ASCII value of their characters.
s1 > s2 True if string s1 comes after s2 based on the ASCII value of their characters.
n1 -eq n2 True if the integers n1 and n2 are algebraically equal.
n1 -ne n2 True if the integers n1 and n2 are not algebraically equal.
n1 -gt n2 True if the integer n1 is algebraically greater than the integer n2.
n1 -ge n2 True if the integer n1 is algebraically greater than or equal to the integer n2.
n1 -lt n2 True if the integer n1 is algebraically less than the integer n2.
n1 -le n2 True if the integer n1 is algebraically less than or equal to the integer n2.
These primaries can be combined with the following operators:
! expression True if expression is false.
expression1 -a expression2
True if both expression1 and expression2 are true.
expression1 -o expression2
True if either expression1 or expression2 are true.
(expression) True if expression is true.
The -a operator has higher precedence than the -o operator.
GRAMMAR AMBIGUITY
The test grammar is inherently ambiguous. In order to assure a degree of consistency, the cases described in IEEE Std 1003.2 (``POSIX.2'')
section 4.62.4, are evaluated consistently according to the rules specified in the standards document. All other cases are subject to the
ambiguity in the command semantics.
RETURN VALUES
The test utility exits with one of the following values:
0 expression evaluated to true.
1 expression evaluated to false or expression was missing.
>1 An error occurred.
STANDARDS
The test utility implements a superset of the IEEE Std 1003.2 (``POSIX.2'') specification.
BSD May 31, 1993 BSD