Read a file in a Bash script

Question

I have a file in my file system. I want to read that file in bash script. File format is different i want to read only selected values from the file. I don't want to read the whole file as the file is very huge. Below is my file format:

Name=TEST
Add=TEST
LOC=TEST

In the file it will have data like above. From that I want to get only Add date in a variable. Could you please suggest me how I can do this.

As of now i am doing this to read the file:

file="data.txt"
while IFS= read line
do
    # display $line or do somthing with $line
    echo "$line"
done < "$file"

Inian · Accepted Answer · 2017-01-12 13:55:51Z

4

Use the right tool meant for the job, Awk in this case to speed things up!

dateValue="$(awk -F"=" '$1=="Add"{print $2; exit}' file)"
printf "%s\n" "dateValue"
TEST

The idea is to split input lines by = as the de-limiter. The awk logic works by checking the $1 field which equals to Add and prints the corresponding value associated with it.

The exit part after print is optional. It will quit the processing as soon as the Add string is met. It will help in quick processing if the file is huge as you have indicated.

edited Jan 12, 2017 at 13:55

answered Jan 12, 2017 at 13:50

Inian

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2 Comments

codeforester Over a year ago

Is exit really optional?

Inian Over a year ago

@codeforester: optional as in, the command will still work as long as there are no similar $1 values in Add. But in a case if it is not present, the command will take too much time to run on a big file, but nevertheless will do the job.

codeforester · Accepted Answer · 2017-01-12 17:05:50Z

2

You could rewrite your loop this way, notice the break after you got your line:

while IFS='=' read -r key value; do
  if [[ $value == "Add" ]]; then
    # your logic
    break
  fi
done < "$file"

If your intention is to just get the very first occurrence of "Add=", then you could use grep this way:

value=$(grep -m 1 '^Add=' "$file" | cut -f2 -d=)

answered Jan 12, 2017 at 17:05

codeforester

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1 Comment

Inian Over a year ago

Appreciate your answering in bash, but it is not really a tool for processing when considering performance, read through unix.stackexchange.com/questions/169716/… for a detailed/well-explained research on this

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