Why does this bash if statement error out?

jmusbach · 10-24-2012, 12:48 PM

I have the following part of a if statement:

Code:

elif [[ (("$ssh_to" = "<server address>") && -n egrep "oneclass_.*" $current_cos && -z egrep "oneclass_.*" ${avail_cos_arr[$(($cos_choice-1))]}) -o (("$ssh_to" = "<server address>") && -n egrep "secondclass_.*" $current_cos && -z egrep "secondclass_.*" ${avail_cos_arr[$(($cos_choice-1))]}) ]]; then

and it seems ok to me, except the following errors are thrown:

Code:

./change_cos.sh: line 100: expected `)'
./change_cos.sh: line 100: syntax error near `"oneclass_.*"'

Why?

Dafydd · 10-24-2012, 01:47 PM

A lot of errors occur because of mistakes before the place designated.

Also are the number of '(' and the number of ')' the same.

Rupadhya · 10-24-2012, 04:46 PM

I think this is really hard to debug as one line, so I split it up the best I can. Here is what I have so far. Please modify this into your script and test some more. I really can't do much more without knowing what the rest of the script does.

Code:

if [[ (("$ssh_to" = "<server_address>")) ]] &&
egrep -n "oneclass_.*" $current_cos &&
egrep -z "oneclass_.*" ${avail_cos_arr[$(( $cos_choice-1)) ]} \
-o "$ssh_to" = "<server address>" &&
egrep -n "secondclass_.*"  \
$current_cos && egrep -z "secondclass_.*" \
${avail_cos_arr[$(($cos_choice-1))]} ]]; then
echo 'It did work'  >> /dev/null
fi

What I did was break this into multiple lines, run it a couple of times and find out where you had extra parenthesis or missing parenthesis. Changed the egrep to
egrep [option] instead of [option] egrep, and ran it again. I don't know if it really works, but it doesn't syntax error out.

- Raj

grail · 10-24-2012, 05:46 PM

@Rupadhya - I think you will find there is a big difference between using the bash test -z and egrep -z:

Code:

man test extract
-z STRING
    the length of STRING is zero

man grep extract
-z, --null-data
    Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option,
    this option can be used with commands like sort -z to process arbitrary file names.

However, I do agree that the process of breaking up the long single line is a good idea

@OP - Any reason why you use && for AND but use -o as opposed to || for OR?

Rupadhya · 10-24-2012, 07:56 PM

Grail,

I agree with you that there is a big difference between the string manipulator -z and the egrep option of egrep -z. My bad for not finding that one out. It is really hard to debug multi process in one line commands. Usually, I break them apart (like above) and then if I really think I can get them to work as one command I put them together. I think in a shell script that you have in a file it really doesn't matter much. Some people like to have the commands all in one line for the ubiquitous one liner that has made *nix so famous. Try to do that on your favorite Windows flavor

.

- Raj