How to expand PS1?

Question

I have a shell script that runs the same command in several directories (fgit). For each directory, I would like it to show the current prompt + the command which will be ru

Answer 1

One more possibility: without editing bash source code, using script utility (part of bsdutils package on ubuntu):

$ TEST_PS1="\e[31;1m\u@\h:\n\e[0;1m\$ \e[0m"
$ RANDOM_STRING=some_random_string_here_that_is_not_part_of_PS1
$ script /dev/null <<-EOF | awk 'NR==2' RS=$RANDOM_STRING
PS1="$TEST_PS1"; HISTFILE=/dev/null
echo -n $RANDOM_STRING
echo -n $RANDOM_STRING
exit
EOF

script command generates a file specified & the output is also shown on stdout. If filename is omitted, it generates a file called typescript.

Since we are not interested in the log file in this case, filename is specified as /dev/null. Instead the stdout of the script command is passed to awk for further processing.

1. The entire code can also be encapsulated into a function.
2. Also, the output prompt can also be assigned to a variable.
3. This approach also supports parsing of PROMPT_COMMAND...