It only works with the first command in the recorded history, not with any sub shells or chained commands.
#!/usr/bin/env bash
# 1. history and $HISTFILE do not work in scripts. Therefore cat with a direct
# path is needed.
# 2. awk gets the first part of the command name.
# 3. List is then sorted and duplicate entries are removed.
# 4. type -P will expand command names to paths, similar to which. But it will
# also expand aliases and functions.
# 5. Final output is then sorted again.
type -P $(cat ~/.bash_history | awk '{print $1}' | sort | uniq) | sort
After reading a blog post, I had this script in mind to see if its possible. This is just for fun and I don’t have an actual use for it. Maybe some parts of it might inspire you to do something too. So have fun.
Edit 1:
After some suggestions from the comments, here is a little shorter version. sort | uniq
can be replaced by sort -u
, as the output of them should be identical in this case (in certain circumstances they can have different effect!). Also someone pointed out my useless cat
, as the file can be used directly with awk
. And for good reason. :D Enjoy, and thanks for all.
type -P $(awk '{print $1}' ~/.bash_history | sort -u) | sort
I still have no real use case for this one liner, its mainly just for fun.
As I’ve been working on an install script for making my setup more portable, this is handy and timely. Thanks for sharing!
PS I hate to be the UUOC person. I’m sure you’re already aware and it was a deliberate choice.
PS I hate to be the UUOC person. I’m sure you’re already aware and it was a deliberate choice.
I wish it was. I honestly forgot. yeah, shame on me. :D Before this, at the position of cat there was actually a different command, which I replaced with this. And I didn’t think of adding the file to awk instead. I’ll update the line with this suggestion and a suggestion from someone else.
Can this one liner determine if program halts too?
That’s impossible, look up the Halting problem
That’s the joke
I’m actually not sure what you mean by that. This script will only list the programs you used in the terminal. It prints the fullpath of each command. That’s all it does.
Do you want know if a program is currently running?
Silly me misunderstood the intention of the script. I imagined it lists the programmatic paths the program can take, like all the decision in the program. :)
sort | uniq can be sort -u instead btw
They are not exactly the same. I always default to piping it, because I never remember which to use when. And had to lookup again to make sure I was not hallucinating: https://unix.stackexchange.com/questions/76049/what-is-the-difference-between-sort-u-and-sort-uniq/76095#76095
Interesting, I never knew. Thanks
I agree they aren’t the same, especially if you need uniq to count things.
However, be aware that pipes can be a real problem in scripts because of globbing and expansion.
Or just use zsh 🫰