Process Exit and Recovery

Exit Status

Decide the Next Step

Shell scripts use exit status values to decide whether later work should continue. Modeling the status keeps the lesson deterministic without exiting the replay.

Program

Play the script to choose a status and see the next-step decision.

status
exit_status_check.sh
Replay: real traced execution (multi-file project)
#!/usr/bin/env bash

status=0
command="validate-config"
if [ "$status" -eq 0 ]; then
    result="continue"
else
    result="stop:$status"
fi
echo "$command:$result"

#!/usr/bin/env bash

status=2
command="validate-config"
if [ "$status" -eq 0 ]; then
    result="continue"
else
    result="stop:$status"
fi
echo "$command:$result"

  1. status ← 0

    3status=04command="validate-config"
    values this step0status

  2. command ← validate-config

    3status=04command="validate-config"5if [ "$status" -eq 0 ]; then
    values this stepvalidate-configcommand

  3. if [ "$status" -eq 0 ]; then

    4command="validate-config"5if [ "$status" -eq 0 ]; then6    result="continue"
    values this step0status

  4. result ← continue

    5if [ "$status" -eq 0 ]; then6    result="continue"7else
    values this stepcontinueresult

  5. echo "$command:$result"

    9fi10echo "$command:$result"
    outputvalidate-config:continue
    values this stepvalidate-configcommandcontinueresult

  1. status ← 2

    3status=24command="validate-config"
    values this step2status

  2. command ← validate-config

    3status=24command="validate-config"5if [ "$status" -eq 0 ]; then
    values this stepvalidate-configcommand

  3. if [ "$status" -eq 0 ]; then

    4command="validate-config"5if [ "$status" -eq 0 ]; then6    result="continue"
    values this step2status

  4. result ← stop:2

    7else8    result="stop:$status"9fi
    values this stepstop:2result2status

  5. echo "$command:$result"

    9fi10echo "$command:$result"
    outputvalidate-config:stop:2
    values this stepvalidate-configcommandstop:2result
exit status An exit status is the numeric result of a command.
zero Status zero conventionally means success.
stop path A nonzero status should usually stop or recover before continuing.