mjhjmtu

I want to assign log output to "line", I tried the following
line=tail -1000 /var/log/syslog

but it doesn't work.

myscript is like below

#!/bin/bash

line=`tail -1000 /var/log/syslog`
d1=$(date --date="-10 min" "+%b %_d %H:%M")
d2=$(date "+%b %_d %H:%M")
while read line; do
 [[ $line > $d1 && $line < $d2 || $line =~ $d2 ]] && echo $line
done

Try this change

fd=""
tmplog="/tmp/temp_$$$_$RANDOM"
tail -1000 /var/log/syslog > “$tmplog”

exec fd<“$tmplog"

while IFS='' read -r -u $fd line || [[ -n $line ]]; do
 #your commands here
done

exec fd>&-
rm "$tmplog"

How it works:
Assign fd as a variable.
Create a temp file using the script PID and the built in “RANDOM” number (you could also use the mktemp command in place of this).
Open the file descriptor fd for reading of the temp file.
Use while loop with IFS set to nothing and run read command with -u option to read from fd.
Put your commands inside the loop using the same line variable.
Close the file descriptor.
Remove the temp file.

Your assignment works fine -- although $( ... ) is more robust and better style than backticks. But read line doesn't read from line, it reads from stdin (the terminal, since you didn't redirect it) into line, destroying the previous contents. Try one of:

data=$(tail -1000 /file) 
while read line; do echo "$line"; done <<<"$data"
# bash ksh zsh but maybe not older shells
# or 
while read line; do echo "$line"; done < <(tail -1000 file)
# ditto 

data=$(tail -1000 /file) 
echo "$data" | while read line; do echo "$line"; done 
# or
tail -1000 file | while read line; do echo "$line"; done
# most shells, but any var set (or other shell change made) within the loop 
# will disappear on _some_ shells because pipelines are run in subshells

with appropriate commands added in the loop.

In general to keep data unmangled by read you need -r as shown by EnterUserNameHere, but syslog entries are pretty structured and shouldn't need it for any case I can think of. OTOH adding it won't hurt and is good practice.

Note comparing datestrings won't work early on the first day of some months; for example if now-10min is "Nov 31 23:55" and now is "Dec 01 00:05" then all of the datestrings that are actually between those two times will fail the test $line > $d1 && $line < $d2