I want to detect if the 1st bash input parameter is "debug"(string).
I write script like this:
#! /usr/bin/env bash
if [ "$#" -eq "1" && "$1" -eq "debug" ]; then
echo "hello debug"
fi
Error message:
line 3: [: missing `]'
I don't know why, please help.
Compare strings with ==, -eq is an arithmetic operator. Also, within [] you have to use the -a operator instead of &&, or split it in two. Here are a few different ways to write the same thing:
if [[ $# -eq 1 && "$1" == "debug" ]] ; then
echo "hello debug"
fi
if [[ "$#" == "1" && "$1" == "debug" ]] ; then
echo "hello debug"
fi
if [ "$#" == "1" ] && [ "$1" == "debug" ] ; then
echo "hello debug"
fi
if [ "$#" == "1" -a "$1" == "debug" ] ; then
echo "hello debug"
fi
Instead of [ "$#" -eq "1" && "$1" -eq "debug" ], use either [ "$#" -eq "1" ] && [ "$1" -eq "debug" ] or [ "$#" -eq "1" -a "$1" -eq "debug" ]. The problem is that && is bash's way of saying "and", rather than -a, which is test's way of saying "and". You can't use a bash "and" inside of test.
Related
I'm learning BASH through HackerRank.There's an exercise in which the lengths of the triangle is given and then you need to find whether the triangle is isosceles,scalene or equilateral.I wrote the following code:
read a
read b
read c
if [ [ "$a" -eq "$b" ] && [ "$b" -eq "$c" ] ]
then
echo "EQUILATERAL"
elif [ [ "$a" -eq "$b" ] || [ "$b" -eq "$c" ] ]
then
echo "ISOSCELES"
else
echo "SCALENE"
fi
But then I get the following error
solution.sh: line 4: [: too many arguments
solution.sh: line 7: [: too many arguments
solution.sh: line 7: [: too many arguments
Why is this happening? I tried long and hard to rectify it but nothing worked out
You can combine conditions either ommiting the surrounding brackets like this
if [ "$a" -eq "$b" ] && [ "$b" -eq "$c" ]
or by combining the conditions with -a/-o like this
if [ "$a" -eq "$b" -a "$b" -eq "$c" ]
see http://wiki.bash-hackers.org/commands/classictest#and_and_or
&& and || are Bash list operators. In a chain of commands, the next command is executed only if the previous command returned 0 (&&) or nonzero (||).
[ is an alias for the Bash internal test command and has arguments such as -eq or -ne. ] ends its command line. Type help test for more information.
So if you write a conditional expression, you do not put the list operators inside brackets.
Try, for example, this instead of the respective line in your code:
if [ "$a" -eq "$b" ] && [ "$b" -eq "$c" ]
then
[ isn't a grouping operator in bash, you can't use it to group tests.
there are a number of different ways to express the tests you want to make, numeric evaluation mode is probably easiest to read
if (( a == b && b == c ))
if (( a == b || b == c || c == a ))
This is going to break if you have decimal fractions, but will work fine for integers.
[ is a conditional command, like an alias for sh's test built-in command.
[[ is the same for bash which has more test options.
So make a choice between [ and [[ but not [ [ which means two command.
Example:
# [ [ -n 'test' ] ]
bash: [: too many arguments
# [ -n 'test' ] && echo $?
0
# [[ -n 'test' ]] && echo $?
0
When I run this bash script :
if [ [$EUID -ne 0] ]; then
echo "This script must be run as root" 1>&2
exit 1
else
printf " whathever "
exit 0
fi
I have this error :
./myScript: 15: [: Illegal number: [
Do you see any problem ?
You have syntax error in your if condition, use this if condition:
if [ "$EUID" -ne 0 ];
OR using [[ and ]]
if [[ "$EUID" -ne 0 ]];
You have syntax error in your if condition, use this if condition:
if [ "$EUID" -ne 0 ];
OR using [[ and ]]
if [[ "$EUID" -ne 0 ]];
If you use the KSH88+/Bash 3+ internal instruction [[, it's not necessary to use doubles quotes around the variables operands :
[ ~/test]$ [[ $var2 = "string with spaces" ]] && echo "OK" || echo "KO"
OK
Instead of the external command test or his fork [ :
[ ~/test]$ [ $var2 = "string with spaces" ] && echo "OK" || echo "KO"
bash: [: too many arguments
KO
[ ~/test]$ [ "$var2" = "string with spaces" ] && echo "OK" || echo "KO"
OK
Of course, you also have to choose the operators according to the type of operands :
[ ~/test]$ var1="01"
[ ~/test]$ [ "$var1" = "1" ] && echo "OK" || echo "KO"
KO
[ ~/test]$ [ "$var1" -eq "1" ] && echo "OK" || echo "KO"
OK
two suggestions apart from what everyone else has pointed out already.
rather than doing else [bunch of code because we are root] fi, just replace the else with fi. once you've tested for the failure condition you are concerned about and taken appropriate action, no need to continue to be within the body of the conditional.
$EUID is a bashism, if you would like to make this portable to shells such as ksh, replacing it with:
if [ $(id -u) -ne 0 ]; then echo "ur not root bro"; exit 1; fi
would be a good way to do it.
using
sudo bash shell_script.sh
instead of
sudo sh shell_script.sh
solved in my case.
I am trying to execute the following shell script
#!/bin/sh
echo "start"
if [ $# != 2 || $1 != "first" || $1 != "second" ]
then
echo "Error"
fi
echo "done"
and I'm getting the following output:
start
./autobuild.sh: line 3: [: missing `]'
./autobuild.sh: line 3: !=: command not found
./autobuild.sh: line 3: !=: command not found
done
I have no idea how to resolve the errors. Even if I use -ne instead of !=, I get the same errors. Please help.
Your syntax is incorrect. If you want multiple conditions in an if statement you need to have multiple [] blocks. Try:
if [ $# != 2 ] || [ $1 != "first" ] || [ $1 != "second" ]
But, it's better to use [[ (if your shell supports it) as it is safer to use. I would go for:
if [[ $# -ne 2 || $1 != "first" || $1 != "second" ]]
See this question on brackets: Is [[ ]] preferable over [ ] in bash scripts?
While OR ing the conditions should be seperate as follows :
#!/bin/sh
echo "start"
if [ $# != 2] || [ $1 != "first" ] || [ $1 != "second" ]
then
echo "Error"
fi
echo "done"
Try substituting -NE for !=.
if-usage samples
This should work:
#!/bin/sh
echo "start"
if [ $# -ne 2 -o $1 -ne "first" -o $1 -ne "second" ]
then
echo "Error"
fi
echo "done"
#!/bin/bash
if [$# -ne 1];
then
echo "/root/script.sh a|b"
else if [$1 ='a'];
then
echo "b"
else if [$1 ='b']; then
echo "a"
else
echo "/root/script.sh a|b"
fi
I'm getting below error while run above script in Linux.
bar.sh: line 2: [: S#: integer expression expected
a
Could you please help to remove this error?
if [$# -ne 1];
[ and ] requires spacing. Example:
if [ $# -ne 1 ];
And else if should be elif
#!/bin/bash
if [ "$#" -ne 1 ];
then
echo "/root/script.sh a|b"
elif [ "$1" ='a' ];
then
echo "b"
elif [ "$1" ='b' ]; then
echo "a"
else
echo "/root/script.sh a|b"
fi
Do not forget to quote variables. It is not every time necessary, but recommended.
Question: Why do i have -1?
Bash doesn't allow else if. Instead, use elif.
Also, you need spacing within your [...] expression.
#!/bin/bash
if [ $# -ne 1 ];
then
echo "/root/script.sh a|b"
elif [ $1 ='a' ];
then
echo "b"
elif [ $1 ='b' ]; then
echo "a"
else
echo "/root/script.sh a|b"
fi
How can I consolidate the following if statements into a single line?
if [ $# -eq 4 ]
then
if [ "$4" = "PREV" ]
then
print "yes"
fi
fi
if [ $# -eq 3 ]
then
if [ "$3" = "PREV" ]
then
print "yes"
fi
fi
I am using ksh.
Why does this give an error?
if [ [ $# -eq 4 ] && [ "$4" = "PREV" ] ]
then
print "yes"
fi
Error:
0403-012 A test command parameter is not valid.
Try this:
if [[ $# -eq 4 && "$4" == "PREV" ]]
then
print "yes"
fi
You can also try putting them all together like this:
if [[ $# -eq 4 && "$4" == "PREV" || $# -eq 3 && "$3" == "PREV" ]]
then
print "yes"
fi
Do you just want to check if the last argument is "PREV"? If so, you can also do something like this:
for last; do true; done
if [ "$last" == "PREV" ]
then
print "yes"
fi
'[' is not a grouping token in sh. You can do:
if [ expr ] && [ expr ]; then ...
or
if cmd && cmd; then ...
or
if { cmd && cmd; }; then ...
You can also use parentheses, but the semantics is slightly different as the tests will run in a subshell.
if ( cmd && cmd; ); then ...
Also, note that "if cmd1; then cmd2; fi" is exactly the same as "cmd1 && cmd2", so you could write:
test $# = 4 && test $4 = PREV && echo yes
but if your intention is to check that the last argument is the string PREV, you might consider:
eval test \$$# = PREV && echo yes
Try this :
if [ $# -eq 4 ] && [ "$4" = "PREV" ]
then
print "yes"
fi