Linux bash script: How to put command line into variable?

Question

I have a questions about bash script, i want to put part of find expression to variable. I show on example better what i want to. I have something like this:

find $DIR -type f -name "$NAME" $SIZE $CONTENT_COM;;

and i want to put into $CONTENT_COM something like this: (exactly like this)

-exec grep -l "$CONTENT" {} +

For $SIZE i made this:

SIZE=${SIZE/$SIZE/-size $SIZE};

and i wanted to make this for $CONTENT_COM (it looks similar to what i want, just change -size $SIZE etc to look like this

CONTENT_COM=${CONTENT_COM/$CONTENT/-exec grep -l "$CONTENT" {} +}

but it doesnt work. ({} +} <---- error in editor) Is there any way to put such expression to variable then use it ?

See BashFAQ #50 -- I'm trying to put a command in a variable, but the complex cases always fail! — Charles Duffy
– Charles Duffy, Commented Mar 27, 2021 at 1:01
Possible duplicate of "Why does shell ignore quoting characters in arguments passed to it through variables?" (which is itself marked as a duplicate, but the other is significantly different). — Gordon Davisson
– Gordon Davisson, Commented Mar 27, 2021 at 2:50

l0b0 · Accepted Answer · 2021-03-27 00:24:44Z

2

Yes, you can use arrays to build up commands with arbitrary arguments, for example:

search_term='some regex'
content_command=('grep' '-l' "$search_term")
find . -exec "${content_command[@]}" {} +

Also, Use More Quotes™!

answered Mar 27, 2021 at 0:24

l0b0

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3 Comments

Kawson Over a year ago

Thanks! It helped me alot. I can't do -exec outside the array because not every time i want to exec it, but solution was for sure a little bit different (from link you post): CONTENT_COM=(( -exec grep -l "$CONTENT" {} + )) [\ before ( and ) but comments delete it]

Charles Duffy Over a year ago

@Kawson, ...that's a bit confusing. It should only be one ( and one ), not doubled, and no backslashes. (Doubling (( and )) is the syntax for starting and ending an arithmetic context; it does a very different thing). The syntax in this answer is exactly correct just as it is.

Gordon Davisson Over a year ago

@Kawson You can use backticks to mark code in comments. Are you trying to include literal parentheses in the array (i.e. to include them in the find expression), like CONTENT_COM=( $ -exec grep -l "$CONTENT" {} + $ )? You shouldn't need to, since the whole -exec ... + expression is a single logical item in the find expression.

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