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Accepted
genderbee
Asked: 2019-10-02 11:28:31 +0800 CST

Bash, grep, whole line as variable

  • 772

Issue

How can I store whole line output from grep as 1 variable, not for every string.

Example (I need just 3 variables, whole lines).

user@local:~/bin/kb$ grep -E '##.*bash.*file.*add' bash.kb
## bash, file, add string behind founded string
## bash, files, add string to begin
## bash, file, add comma to end of line except last line
user@local:~/bin/kb$

But for example.

user@local:~/bin/kb$ for i in $(grep -E '##.*bash.*file.*add' bash.kb); do echo $i; done
##
bash,
file,
add
string
behind
founded
string
##
bash,
files,
add
string
to
begin
##
bash,
file,
add
comma
to
end
of
line
except
last
line
user@local:~/bin/kb$

I need this (only 3 variables as whole line).

1st variable $i[0] = '## bash, file, add string behind founded string'
2nd variable $i[1] = '## bash, files, add string to begin'
3rd variable $i[2] = '## bash, file, add comma to end of line except last line'

How can I do that?

Thanks.

bash sed grep

1 Answers

  1. Best Answer

    Your issue is that

    for i in $(grep -E '##.*bash.*file.*add' bash.kb); do echo $i; done

    iterates over whitespace-delimited words in the command output. This is sometimes referred to as word splitting or more generally as split + glob.

    You can read lines into an indexed array in bash using mapfile (or its synonym, readarray). Because mapfile reads from standard input, replace the command substitution $( ... ) with a process substitution <( ... ):

    mapfile -t var < <(grep -E '##.*bash.*file.*add' bash.kb)

    You can retrieve the values using "${var[0]}","${var[1]}" etc. (arrays are zero-based) or loop over them all using 

    for i in "${var[@]}"; do echo "$i"; done

    Note the use of double quotes to prevent word-splitting within the array elements.

    If you don't actually need variables at all, and simply want to loop over the lines of command output, then use a while loop in place of a for loop:

    while read -r i; do
  echo "$i"
done < <(grep -E '##.*bash.*file.*add' bash.kb)
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