Grep multiple bash parameters

Question

I'm writing a bash script which shall search in multiple files.

The problem I'm encountering is that I can't egrep an undetermined number of variables passed as parameters to the bash script

I want it to do the following:

Given a random number of parameters. i.e:

./searchline.sh A B C

Do a grep on the first one, and egrep the result with the rest:

grep "A" * | egrep B | egrep C

What I've tried to do is to build a string with the egreps:

for j in "${@:2}";
do
ADDITIONALSEARCH="$ADDITIONALSEARCH | egrep $j";
done

grep "$1" * "$ADDITIONALSEARCH"

But somehow that won't work, it seems like bash is not treating the "egrep" string as an egrep.

Do you guys have any advice?

By the way, as a side note, I'm not able to create any auxiliary file so grep -f is out of the line I guess. Also note, that the number of parameters passed to the bash script is variable, so I can't do egrep "$2" | egrep "$3".

Thanks in advance.

Fernando

@fedorqui: '|' means OR, not and. When you pipe egrep, you want the intersection of the patterns, so an AND. — Bentoy13
– Bentoy13, Commented Aug 8, 2013 at 12:20

Yorik.sar · Accepted Answer · 2013-08-08 13:05:36Z

4

You can use recursion here to get required number of pipes:

#!/bin/bash

rec_egrep() {
    if [ $# -eq 0 ]; then
        exec cat
    elif [ $# -eq 1 ]; then
        exec egrep "$1"
    else
        local pat=$1
        shift
        egrep "$pat" | rec_egrep "$@"
    fi
}

first_arg="$1"
shift
grep "$first_arg" * | rec_egrep "$@"

answered Aug 8, 2013 at 13:05

Yorik.sar

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Comments

konsolebox · Accepted Answer · 2024-03-29 13:23:46Z

3

A safe eval can be a good solution:

#!/bin/bash

if [[ $# -gt 0 ]]; then
    temp=(egrep -e "\"\$1\"" '*')

    for (( i = 2; i <= $#; ++i )); do
        temp+=('|' egrep -e "\"\${$i}\"")
    done

    eval "${temp[@]}"
fi

To run it:

bash script.sh A B C

edited Mar 29, 2024 at 13:23

answered Aug 8, 2013 at 12:24

konsolebox

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3 Comments

Gordon Davisson Over a year ago

Wow, a use of eval that (at least as far as I can see) actually is safe! +1 for you, sir.

Charles Duffy Over a year ago

What's the value of defining temp as an array when eval is just going to concatenate it back into a single string before running that string through the parser?

konsolebox Over a year ago

@CharlesDuffy Preference. Also I think it's more efficient when the list of elements grows. A list is better that a repeatedly concatenated string. Also I might just use normal variables sometimes. Either method is fine. It's just up to you which you think is more convenient to write, although this time I think the use of an array is better.

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