f()

You all, of course, know about the fc command. From bash’s help system:

fc: fc [-e ename] [-nlr] [first] [last] or fc -s [pat=rep] [cmd]

fc is used to list or edit and re-execute commands from the history list. FIRST and LAST can be numbers specifying the range, or FIRST can be a string, which means the most recent command beginning with that string.

Now I had the following problem: you have a file with shell commands in it. Next you want to select a few lines from this file to be executed in your running shell. A way to do this is:

• edit the file with vi
• save this edited file under a different name, say $file
• execute it: . $file

But this is cumbersome and I wanted the executed lines to be added to my shell’s history. So that is why I created the function: f():

• edit a file, exec what’s left
• you are finished editing
• add what is executed to the history (fc -R)

It needs to be a shell function, because as an external executable you cannot alter your current shell history.

Synopsis: f filename

This is the body of the function:

f() {
if [[ ! -f $1 ]]; then return 1; fi

copy=$(mktemp ${TMPPREFIX:-/tmp/shell}.XXXXXXX)
if cp $1 $copy; then
    if ${EDTIOR:-vi} $copy; then
	$SHELL $copy
	# add to hist
	fc -R ${copy}
	rm -f $copy
    fi
   else
    return 1
fi
}

How does it work?

• Check if we have an argument
• If so, copy the file to a temporary file
• Edit this temporary file
• Execute the contents when the editor did a normal exit
• Add the results to the current history (fc -R)
• Remove the temporary file