CODEWITHSUNDEEP
bashshellwc
Marcin Kulik
Marcin Kulik

Reputation: 983

wc does not return an integer value - integer expression expected

I am trying to run this script:

#!/bin/sh
cd $1
for i in */*.$2
do
   if [ 'wc –c $i' -gt $3 ]
   then
       chmod o-r $i
   fi
done

When I run the script: 

./script folder1 txt 500

I get this error:

./script: line 5: [: wc –c $i: integer expression expected
./script: line 5: [: wc –c $i: integer expression expected

Any ideas why wc is not returning an integer value?

I am using GNU bash, version 4.4.12(1)-release (x86_64-apple-darwin16.3.0)

Upvotes: 2

Views: 6824

Answers (1)

Mark Reed
Mark Reed

Reputation: 95315

You're using the wrong quotation marks. The code you are copying has backticks (`) around the wc command, not apostrophes ('). (The backtick is the key to the left of the number 1 on a US keyboard.)

But you should avoid using those anyway, because they have some confusing side effects that show up in nested commands; they are only there for backward compatibility, since they were the only way to do command substitution in the earliest UNIX shells. In a modern shell, use $(...) instead. You should also double-quote all your parameter expansions:

# any POSIX shell
if [ "$(wc -c <"$i")" -gt "$3" ]; then
...
fi

(I replaced wc -c "$i" with wc -c <"$i" because, as Gordon notes in the comments, wc outputs the filename along with the count; feeding the file as input means it has no filename to go by and outputs just the bare number we're looking for.)

In bash or ksh I would go one step further and use ((...)) for arithmetic comparison instead of [...]; that way you can use the normal inequality operators like > instead of -gt and friends:

# bash/ksh
if (( "$(wc -c <"$i")" > "$3" )); then
 ...
fi

The standalone ((...)) notation (as opposed to arithmetic expansion $((...)) ) is not part of POSIX, so not present in other shells. A version of it is also supported by zsh, but it's pickier about its numbers and won't work unless you get rid of the quotation marks - which works as long as the file in $i exists and $3 contains a legal number:

# zsh 
if (( $(wc -c <"$i") > $3 )); then
...
fi

Upvotes: 6

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