How to clean up temporary files in Bash with trap

Temporary workspaces let shell scripts assemble reports, archives, or converted data without mixing partial files into the final destination. A script that exits before its last command can leave that workspace behind unless cleanup is tied to the shell lifecycle.

The Bash EXIT pseudo-signal runs its trap before the shell terminates. Capturing $? at the start of the handler preserves the pending result, so a failed workload still reports failure after its files are removed.

The mktemp command creates an unpredictable directory name and prints the resulting path. Initializing the variable before trap registration, checking that it is nonempty, and requiring an existing directory constrain recursive removal to the workspace created by the script.

1. Initialize temp-cleanup.sh for strict execution before trap registration.

   temp-cleanup.sh

   #!/usr/bin/env bash
   set -euo pipefail
    
   mode=${1:-ok}
   workdir=

   Initializing workdir keeps the later guard valid if the shell exits before mktemp assigns a path.

2. Add the cleanup function before the workload.

   cleanup() {
       local status=$?
       trap - EXIT
    
       if [[ -n $workdir && -d $workdir ]]; then
           rm -rf -- "$workdir"
           printf 'removed %s\n' "$workdir"
       fi
    
       exit "$status"
   }

   The quoted rm operand receives only the path stored by mktemp after both guards succeed. Recursive removal can destroy unrelated data if the variable is assigned from another source.

3. Register cleanup for the shell's EXIT pseudo-signal.

   trap cleanup EXIT

4. Append the report workload after trap registration.

   workdir=$(mktemp --directory "${TMPDIR:-/tmp}/report-cleanup.XXXXXX")
   printf 'created %s\n' "$workdir"
   printf 'report data\n' > "$workdir/report.txt"
    
   if [[ $mode == fail ]]; then
       printf 'simulated failure\n' >&2
       false
   fi
    
   printf 'finished work\n'

   The fail argument supplies a controlled nonzero path for testing the handler; the default path reaches the final success message.

5. Compare temp-cleanup.sh with the consolidated file.

   temp-cleanup.sh

   #!/usr/bin/env bash
   set -euo pipefail
    
   mode=${1:-ok}
   workdir=
    
   cleanup() {
       local status=$?
       trap - EXIT
    
       if [[ -n $workdir && -d $workdir ]]; then
           rm -rf -- "$workdir"
           printf 'removed %s\n' "$workdir"
       fi
    
       exit "$status"
   }
    
   trap cleanup EXIT
    
   workdir=$(mktemp --directory "${TMPDIR:-/tmp}/report-cleanup.XXXXXX")
   printf 'created %s\n' "$workdir"
   printf 'report data\n' > "$workdir/report.txt"
    
   if [[ $mode == fail ]]; then
       printf 'simulated failure\n' >&2
       false
   fi
    
   printf 'finished work\n'

6. Check temp-cleanup.sh for Bash syntax errors.

   $ bash -n temp-cleanup.sh

7. Run the default success path.

   $ bash temp-cleanup.sh
   created /tmp/report-cleanup.xAawk7
   finished work
   removed /tmp/report-cleanup.xAawk7

8. Confirm the successful run's printed directory is absent.

   $ ls -ld /tmp/report-cleanup.xAawk7
   ls: cannot access '/tmp/report-cleanup.xAawk7': No such file or directory

9. Run the controlled failure path.

   $ bash temp-cleanup.sh fail
   created /tmp/report-cleanup.wc7Ege
   simulated failure
   removed /tmp/report-cleanup.wc7Ege

10. Print the failed run's retained exit status.

    $ printf 'exit_status=%d\n' "$?"
    exit_status=1

    Status 1 shows that cleanup did not convert the failed workload into a successful script result.

11. Confirm the failed run's printed directory is absent.

    $ ls -ld /tmp/report-cleanup.wc7Ege
    ls: cannot access '/tmp/report-cleanup.wc7Ege': No such file or directory