How to separate output for each command generated by a bash file? - linux

Question

Let's say we have a bash script like the one bellow:
echo test
ls -alh
pwd
echo test2
So the file can have any number of commands on it each producing or not its own output.
Then the above file is run like this /bin/bash -xe test.sh which will produce the following output:
+ echo test
test
+ ls -alh
total 32
drwx------+ 6 daniels staff 204B Apr 3 23:33 .
drwxr-xr-x+ 64 daniels staff 2.1K Apr 4 01:53 ..
-rw-r--r--# 1 daniels staff 6.0K Apr 3 23:33 .DS_Store
drwxr-xr-x 5 daniels staff 170B Mar 15 17:03 Todo
-rw-r--r--# 1 daniels staff 282B Apr 3 20:39 test.py
-rw-r--r--# 1 daniels staff 97B Apr 4 01:52 test.sh
+ pwd
/Users/daniels/Desktop
+ echo test2
test2
Is there any way to parse the generated output reliable and figure out how to separate the output based on each command?
For the above example we should be able to separate and extract one group with:
+ echo test
test
another one with
+ ls -alh
total 32
drwx------+ 6 daniels staff 204B Apr 3 23:33 .
drwxr-xr-x+ 64 daniels staff 2.1K Apr 4 01:53 ..
-rw-r--r--# 1 daniels staff 6.0K Apr 3 23:33 .DS_Store
drwxr-xr-x 5 daniels staff 170B Mar 15 17:03 Todo
-rw-r--r--# 1 daniels staff 282B Apr 3 20:39 test.py
-rw-r--r--# 1 daniels staff 97B Apr 4 01:52 test.sh
etc.
I was thinking of parsing the output and look if the line starts with + then take that as the start of one command but then you can easily have something like echo + ok which will make this logic fail.
Another option would've been if we can modify the char that is outputted by /bin/bash -x so that instead of + to output something like https://en.wikipedia.org/wiki/Delimiter#ASCII_delimited_text but looks like + is hardcoded in bash and not configurable.
Any ideas?

Answer 1

+ is not hard-coded, and this is readily described in man bash and under help set for -x:
-x After expanding each simple command, for command,
case command, select command, or arithmetic for
command, display the expanded value of PS4, fol‐
lowed by the command and its expanded arguments or
associated word list.
And here's a further description of PS4, also from man bash:
PS4 The value of this parameter is expanded as with PS1 and
the value is printed before each command bash displays
during an execution trace. The first character of PS4 is
replicated multiple times, as necessary, to indicate mul‐
tiple levels of indirection. The default is ``+ ''.
Here's an example:
$ PS4=$'\nAnd now, a word from '; set -x; date; uptime
And now, a word from date
Mon Apr 3 16:20:35 PDT 2017
And now, a word from uptime
16:20:35 up 65 days, 1:24, 6 users, load average: 1.20, 1.42, 1.37
You can use this to embed special markers or characters as you see fit.