How do I edit the output of a bash script before executing it?

Question

For example look at the following line of bash-code

eval `echo "ls *.jpg"`

It lists all jpgs in the current directory. Now I want it to just print the line to the prompt so I can edit it before executing. (Like key-up does for example)

How do I do that?

---

The reason for this question comes from a much more usefull alias:

alias ac="history 2 | sed -n '1 s/[ 0-9]*//p' >> ~/.commands; sort -fu ~/.commands > ~/.commandsTmp; mv ~/.commandsTmp ~/.commands"
alias sc='oldIFS=$IFS; IFS=$'\n'; text=(); while read line ; do text=( ${text[@]-} "${line}") ; done < ~/.commands; PS3="Choose command by number: " ; eval `select selection in ${text[@]}; do echo "$selection"; break; done`; IFS=$oldIFS'
alias rc='awk '"'"'{print NR,$0}'"'"' ~/.commands; read -p "Remove number: " number; sed "${number} d" ~/.commands > ~/.commandsTmp; mv ~/.commandsTmp ~/.commands'

Where ac adds or remembers the last typed command, sc shows the available commands and executes them and rc deletes or forgets a command. (You need to touch ~/.commands before it works)

It would be even more usefull if I could edit the output of sc before executing it.

Answer 1

history -s whatever you want

will append "whatever you want" to your bash history. Then a simple up arrow (or !! followed by enter if you have shopt histreedit enabled --- I think that's the option I'm thinking of, not 100% sure), will give you "whatever you want" on the command line, ready to be edited.

Answer 2

Some comments on your aliases:

Simplified quoting:

alias rc='awk "{print NR,\$0}" ~/.commands ...'

No need for tail and you can combine calls to sed:

alias ac="history 2 | sed -n '1 s/[ 0-9]*//p'..."

Simplified eval and no need for $IFS:

alias sc='text=(); while read line ; do text+=("${line}") ; done < ~/.commands; PS3="Choose command by number: " ; select selection in "${text[@]}"; do eval "$selection"; break; done'

Answer 3

@OP, you should really put those commands into subroutines, and when you want to use them, source it. (taken from dennis's answers)

rc(){
 awk "{print NR,\$0}" ~/.commands ...
}

ac(){
 history 2 | sed -n '1 s/[ 0-9]*//p'...
}

sc(){
 text=()
 while read line
 do 
     text+=("${line}") 
 done < ~/.commands
 PS3="Choose command by number: " 
 select selection in "${text[@]}" 
 do 
     eval "$selection"
     break
 done
}

then save it as "library.sh" or something and when you want to use it

$ source /path/to/library.sh  

Or

$ . /path/to/library.sh  

Answer 4

Maybe you could use preexec.bash?

http://www.twistedmatrix.com/users/glyph/preexec.bash.txt

(On a related note, you can edit the current command line by using ctrl-x-e as well!)

cheers,

tavod