Write to file from within a for loop in Bash

Question

Let's say I have the following csv file:

A,1
A,2
B,3
C,4
C,5

And for each unique value i in the first column of the file I want to write a script that does some processing using this value. I go about doing it this way:

CSVFILE=path/to/csv
VALUES=$(cut -d, -f1 $CSVFILE | sort | uniq)

for i in $VALUES;
do
cat >> file_${i}.sh <<-!
#!/bin/bash
#
# script that takes value I
#
echo "Processing" $i
!
done

However, this creates empty files for all values of i it is looping over, and prints the actual content of files to the console.

Is there a way to redirect the output to the files instead?

what's your target idea on those values? post what should be the final result — RomanPerekhrest
– RomanPerekhrest, Commented Oct 17, 2019 at 11:42
$CSVFILE=path/to/csv is an error. You likely wanted CSVFILE=path/to/csv? Also, -f4 does not exist in your CSV sample, did you mean -f1? With those changes, I am getting file_A.sh, file_B.sh and file_C.sh with the quoted content, not empty files. — Amadan
– Amadan, Commented Oct 17, 2019 at 11:42
I agree with @Amadan : Voting to close as a typo, but glad your problem is resolved. If still trouble, try cat - >> file <<-! (note the - added after cat). Good luck to all. — shellter
– shellter, Commented Oct 17, 2019 at 12:36
thank you @Amadan, I corrected the typo in the example, but it seems it's not a good reproducible example of my problem because in my original code I am still getting the output in the console and the "bad substitution" error, so I assume it's something in my script that's not playing well with capturing the output of cat... — anamaria
– anamaria, Commented Oct 17, 2019 at 12:44
If your minimal reproducible example is not reproducible, there's really nothing we can do though. — Amadan
– Amadan, Commented Oct 17, 2019 at 12:46

Akhil · Accepted Answer · 2019-10-17 12:02:38Z

3

Simply

#!/bin/bash

FILE=/path/to/file

values=`cat $FILE | awk -F, '{print $1}' | sort | uniq | tr '\n' ' '`

for i in $values; do
 echo "value of i is $i" >> file_$i.sh
done

Screenshot

answered Oct 17, 2019 at 12:02

Akhil

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mickp · Accepted Answer · 2019-10-17 11:48:03Z

0

Try using this:

#!/usr/bin/env bash    

csv=/path/to/file

while IFS= read -r i; do
cat >> "file_$i.sh" <<-eof
#!/bin/bash
#
# Script that takes value $i ...
#
eof
done < <(cut -d, -f1 "$csv" | sort -u)

answered Oct 17, 2019 at 11:48

mickp

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