Bash script does not output any data in tempfile

Question

This is the code i use, i want to collect data from 4 logfile(s) in one file, then sort it and print the temp filename.

#!/bin/bash

TEMPFILE=$(mktemp)
USER=$1

# Check for input
#if [ -z $1 ]; then echo "Give me one username or mail address please..."

# Fill file with user history
cat /var/log/messages | grep $USER >> $TEMPFILE
cat /var/log/maillog | grep $USER >> $TEMPFILE
zcat /var/log/messages*gz | grep $USER >> $TEMPFILE
zcat /var/log/maillog*gz | grep $USER >> $TEMPFILE

# Sort by date
cat $TEMPFILE | sort -k1M -k2n -k3n > $TEMPFILE

echo $TEMPFILE

anubhava · Accepted Answer · 2015-07-27 11:13:18Z

1

cat and zcat everywhere are useless and you cannot redirect to same file you're reading, that will get you a 0 byte file.

Try this:

#!/bin/bash

TEMPFILE=$(mktemp)
user="$1"

# Check for input
#if [ -z $1 ]; then echo "Give me one username or mail address please..."

# Fill file with user history
grep "$user" /var/log/messages >> $TEMPFILE
grep "$user" /var/log/maillog >> $TEMPFILE
zgrep "$user" /var/log/messages*gz >> $TEMPFILE
zgrep "$user" /var/log/maillog*gz >> $TEMPFILE

# Sort by date
sort -k1M -k2n -k3n "$TEMPFILE" > "$TEMPFILE.tmp"
mv "$TEMPFILE.tmp" "$TEMPFILE"

cat "$TEMPFILE"

PS: Don't use upper case USER as variable run otherwise you will overwrite shell provide value for this variable. In general it is not recommended to use all uppercase variables in your script.

answered Jul 27, 2015 at 11:13

anubhava

790k67 gold badges603 silver badges671 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

cdarke Over a year ago

You could do both grep in one command, same with zgrep and you could mess with stdout so you don't get multiple opens, but it would make the script more difficult to read and I doubt it would save you much, if anything. Only other thing, the question wants to print the temporary file name but you print (cat) the file itself.

anubhava Over a year ago

Thanks for your suggestions. Last echo wasn't serving any purpose as that could be done right after mktemp command. I assumed OP wants to see the final output that's why cat instead of echo

Collectives™ on Stack Overflow

Bash script does not output any data in tempfile

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related