reading a file using shell script

Question

I have a text file named sqlfile, with the following content:

a.sql
b.sql
c.sql
d.sql

What I want is that to store them in variables and then print using for loop. But here I get only d.sql in the output of the script.

The script:

#!/bin/bash

while read line
do
files=`echo $line`
done < /home/abdul_old/Desktop/My_Shell_Script/sqlfile

for file in $files
        do
                echo $file
        done

score 6 · Answer 1 · answered Jan 16 '12 at 06:26

6

A variable can only hold one element, what you want is an array

#!/bin/bash

while read line
do
  files+=( "$line" )
done < /home/abdul_old/Desktop/My_Shell_Script/sqlfile

for file in "${files[@]}"
do
  echo "$file"
done

answered Jan 16 '12 at 06:26

SiegeX

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score 5 · Answer 2 · edited May 23 '17 at 11:45

while read line
do files="$files $line"
done < /home/abdul_old/Desktop/My_Shell_Script/sqlfile

or

files=$(</home/abdul_old/Desktop/My_Shell_Script/sqlfile)

or

files=$(cat /home/abdul_old/Desktop/My_Shell_Script/sqlfile)

You're doing way too much work in your loop.

The middle alternative works with bash; the other two work with most shells. Prefer $(...) to back-quotes.

This code assumes there are no spaces in file names to mess things up. If you do use blanks in file names, you have to work marginally harder - see the array-based solution by SiegeX

score 0 · Answer 3 · edited May 23 '17 at 12:01

0

Using read is fine but you have to set the IFS environment variable first else leading and trailing white space are removed from each line: Preserving leading white space while reading>>writing a file line by line in bash.

edited May 23 '17 at 12:01

Community

1
1

answered Aug 27 '13 at 17:42

John

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Aleks-Daniel Jakimenko-A. · Answer 4 · 2014-07-04T11:08:20.083

All you have to do is:

readarray myData < sqlfile

This will put file lines into an array called myData
Now you can access any of these lines like this:

printf "%s\n" "${myData[0]}" #outputs first line
printf "%s\n" "${myData[2]}" #outputs third line

And you can iterate over it:

for curLine in "${myData[@]}"; do
    echo "$curLine"
done

Note that these lines would contain \n character as well. To remove trailing newlines you can use -t flag like this:

readarray -t myData < sqlfile

readarray is a synonym to mapfile. You can read about it in man bash

score 0 · Answer 5 · edited Jan 16 '12 at 06:30

0

I think you need to make the "files" as array. otherwise, as soon as the while finishes, "files" stores the latest "line". try:

files=( "${files[@]}" $line )

edited Jan 16 '12 at 06:30

Dan

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answered Jan 16 '12 at 06:29

hhwangcocora

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5

score 0 · Answer 6 · answered Jan 16 '12 at 06:36

0

That's right, you assifn last value to "files"

You must use for instance += instead of =

#!/bin/bash

while read line
do
files+=`echo " $line"`
done < /home/abdul_old/Desktop/My_Shell_Script/sqlfile

for file in $files
        do
                echo $file
        done

answered Jan 16 '12 at 06:36

Odobenus Rosmarus

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2
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You don't need the first `echo`; you could perfectly well use `files+=" $line"` and it would be simpler and more efficient (no subshell). – Jonathan Leffler Jan 16 '12 at 06:49
@AbdulManaf: are you using `bash`? Which version of `bash` (find out with `bash --version`). – Jonathan Leffler Jan 16 '12 at 06:49
GNU bash, version 4.1.5(1)-release (i686-pc-linux-gnu) – Abdul Manaf Jan 16 '12 at 07:26
I use GNU bash, version 4.2.10(1)-release (x86_64-pc-linux-gnu), and += works for me. But the point is -- you must not reassign the variable. You need to add new value. If += doesn't work for you , you can try for instance files="$files $line" – Odobenus Rosmarus Jan 17 '12 at 15:04

reading a file using shell script

6 Answers6