Bash delete file when variable = x

bashbash-scriptingshell-scriptsyntax

I'm creating a bash script which reboots the system at each reboot it adds a new line to a text file, I then read the text file before each reboot. Once the variable holding the number of lines reaches say 10 I want the script to delete the text file (at which point on the next reboot it will see the file isn't there, break the loop and prompt the user to start again). I've tried this:

exec < text.txt
nol=0
while read line
do
nol=`expr $nol + 1`
done

reboot_count=10
if ["$nol" == "$reboot_count"];
then
rm text.txt
fi

but this doesn't seem to be working, all help is appreciated 🙂

Best Answer

[ is a command (an alias for test, in fact). You should separate it by whitespace from the surrounding text.

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Bash – Iterating Over Lines in a Variable

With bash, if you want to embed newlines in a string, enclose the string with $'':

$ list="One\ntwo\nthree\nfour"
$ echo "$list"
One\ntwo\nthree\nfour
$ list=$'One\ntwo\nthree\nfour'
$ echo "$list"
One
two
three
four

And if you have such a string already in a variable, you can read it line-by-line with:

while IFS= read -r line; do
    echo "... $line ..."
done <<< "$list"

Bash Script: Redirecting to file gives “Illegal Instruction”

The $EXECUTE >> $REDIRECT statement is not on line 6 in the script. So the error is not in the script but rather in the executable.

...: line 6: 11927 Illegal instruction: 4 $EXECUTABLE >> $OUTFILE

This is also easy to see because or the error text. "Illegal instruction" means that the CPU can not execute some command. It is theoretically possible, but bash is stable software and these error do not occur in mature software.

The text you replaced with an ellipsis usually contains the executable which died or threw an error. I bet 50 rep it wasn't "bash".

Best Answer

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Bash – Iterating Over Lines in a Variable

Bash Script: Redirecting to file gives “Illegal Instruction”

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