Record exit codes of all shell commands as they are executed

Question

I would like to record the exit code of all shell commands from a specific TTY without additional syntax per command.

For example:

> source solution.sh # sets up this bash session to monitor exit codes
> ls
> ls f
ls: f: No such file or directory
> echo "hello world"

Some file would store exit codes:

0
1
0

Is this possible? If not, I am open to other ideas that might accomplish something similar.

My end goal is to collect data on all of my executed commands and their exit codes (kind of like ~/.bash_history with exit codes appended)

I can't think of any straightforward way to do this. Also, if you have a command with subcommands, like an `if` block, do you want to save the exit codes of the subcommands and also the whole block? — Barmar, Jun 04 '20 at 17:40
What larger problem are you really trying to solve with this? Maybe there's a better way to achieve it. — Barmar, Jun 04 '20 at 17:40
I am trying to collect historical data on shell commands and their exit status. — ben-albrecht, Jun 04 '20 at 17:43
Found some interesting ideas of here, but it has the unfortunate side effect of messing up the user's history: https://unix.stackexchange.com/a/158697/352331 — ben-albrecht, Jun 04 '20 at 17:44
@Barmar - Process accounting may be what I'm looking for - I'll have to read up more on it before I can say for sure though. Thanks for the pointer! — ben-albrecht, Jun 04 '20 at 17:49
@thatotherguy - could you elaborate with a small example maybe? — ben-albrecht, Jun 04 '20 at 17:50
I believe [this link](https://stackoverflow.com/questions/962255/how-to-store-standard-error-in-a-variable/52587939#52587939) was provided previously to consider options — vgersh99, Jun 04 '20 at 17:56
Can you use simply : `PROMPT_COMMAND='echo $? >> ~/exit-codes.log'` ? — Philippe, Jun 04 '20 at 18:42

ben-albrecht · Accepted Answer · 2020-06-05T11:36:03.793

0

Thanks to the numerous helpful comments, I have arrived at the following solutions to record exit codes of shell commands as they are executed:

Using trap debug:

trap 'x=$?; $x >> ~/exit-codes.log' DEBUG

Using PROMPT_COMMAND:
```
PROMPT_COMMAND='x=$?; echo $x >> ~/exit-codes.log; (exit $x)'
```
Note that the PROMPT_COMMAND must exit with the exit code in order to preserve exit code history across shell commands.
Process accounting is a more principled solution for this, but it requires sudo access to enable.

The solution.sh I ended up using to log both exit codes and commands is the following:

trap 'previous_exit_code=$?; previous_command=$this_command; \
  this_command=$BASH_COMMAND; [ ! -z "$previous_command" ] && \ 
  echo \"$previous_command\", $previous_exit_code >> ~/exit-codes.log' DEBUG

edited Jun 05 '20 at 11:36

answered Jun 04 '20 at 20:03

ben-albrecht

1,785
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You can write `PROMPT_COMMAND='x=$?; echo $x >> ~/exit-codes.log; (exit $x)'` to preserve the exit status. – chepner Jun 04 '20 at 20:46
@chepner - oh nice. Any other advantages to using PROMPT_COMMAND over trap DEBUG beyond conciseness? – ben-albrecht Jun 04 '20 at 20:48
1

It's not really any more concise; I just used shorter variable names :) – chepner Jun 04 '20 at 20:55
With `PROMPT_COMMAND='x=$?; echo x${x}x >> ~/exit.txt'`, I can do in my shell: `(exit 42)` followed by `echo $?` which prints 42. That's without the `(exit $x)` in bash 4.4.19(1). – Philippe Carphin Aug 17 '23 at 19:35

score -1 · Answer 2 · answered Jun 04 '20 at 18:51

-1

The last exit code is stored in the $? variable.

But then you have to check it for each issued commands so that still needs some glue to achieve your goal I guess.

answered Jun 04 '20 at 18:51

antoine

1,653
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Yes, the glue is the part I was trying to figure out here. I have posted a solution based on feedback in the comments. – ben-albrecht Jun 04 '20 at 20:36

Record exit codes of all shell commands as they are executed

2 Answers2