CODEWITHSUNDEEP
bashshellsh
mehdi
mehdi

Reputation: 147

How to read while reading from a file in bash

i want to use read cmd in a while that read line per line from a file, but i have a problem in line 4 in this script : 

while read a
do
    echo before
    read var
    echo after
done < file1

the result is : 

before
after.

Can you help me to fix this problem????

Upvotes: 1

Views: 1439

Answers (1)

kojiro
kojiro

Reputation: 77107

A file descriptor can really only point to one file at a time. Every invocation of read you have there reads from standard input, including the one in the middle. If you want to read from something else, you have to tell read to use another file descriptor.

exec 5< file1 # assign file1 to the file descriptor number 5.
              # ("open for reading" as it were)
while read <&5 a; do # read from fd5
  echo before
  read var # read from fd0
  echo after
done
exec 5<&- # Reset fd 5 ("close the file" as it were)

You can also use read -u 5 to read from a specific descriptor in bash.

Upvotes: 3

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