I am writing a shell script in which I have a loop. As the loop goes through different values get assigned to the variable i . I want to echo all the values that get i gets assigned each time the loop runs, into a text file.
What I am doing is at the moment is:
echo " $i " > fail
but that only gets me the last value that was assigned to i .
Instead of redirecting the individual echo to your file, redirect the entire loop to the file. This is considerably more efficient, and truncates the file only once, when the loop is started.
for i in "${whatever[@]}"; do
echo " $i"
done >fail
If you don't want to truncate the file at all, of course, you can use >>fail in the same position.
If you use
echo " $i" >> fail
It will append it to the file.
Put
echo " $i " >> fail
within the loop.
echo " $i" > fail Will write to the file (overwrite)
echo " $i" >> fail Will append to the existing file
...command... >>file inside a loop re-opens the file every time the loop is executed, with the obvious performance/efficiency impact.