10 ms·

I learned about `command -v` just now reading this article. I only knew of `which` and `type` (as well as the very convenient `=executable` syntax that expands

by simias 5y ago

I learned about `command -v` just now reading this article. I only knew of `which` and `type` (as well as the very convenient `=executable` syntax that expands to the path of the binary, but I think that's a zsh-ism). What makes `command -v` not machine friendly? It seems to always output just the PATH, unlike type which tries to be human friendly.

guerrilla 5y ago
It's pretty much useless for the same purpose: $ which ls /usr/bin/ls $ type ls ls is aliased to `ls --color=auto' $ command -v ls alias ls='ls --color=auto' Suddenly I find myself irritated at Debian despite not even using it. Why would they not just include the GNU one?
- jwmhjwmh 5y ago
  I think aliases are only used in interactive shells: $ sh -c 'command -v ls' /bin/ls
- scbrg 5y ago
  This is a very unlikely output when run from a script using the /bin/sh interpreter on Debian, though. If that is the output you've gone out of your way to create an alias in a script, in which case it's reasonable output. It is what will happen when the script runs that command, after all.
  - guerrilla 5y ago
    I'm certain there's masses of code that depends on `which` responding the way it does and scripts with aliases in them regardless of whether that was the right way to do it or not, so your point is probably irrelevant in the grand scheme of things. Think about all that enterprise install and setup crap. People still depend on that spaghetti trash working.
- Taywee 5y ago
  That depends on whether your shell has a built-in which or not. Mine says % which ls ls: aliased to /bin/ls --color=auto Which makes way more sense. Your "which" is not telling you what will actually be executed when you run the `ls` command there. `command`, on the other hand, is guaranteed to be a built-in, has consistent behavior, and has defined, consistent output, unlike `which`. What `which` outputs will be different depending on shell and what implementation of `which` you actually have installed.
  - guerrilla 5y ago
    That depends on which which you mean. Which on GNU has always been this: NAME which - shows the full path of (shell) commands. DESCRIPTION Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been executed when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment vari‐ able PATH using the same algorithm as bash(1).
    - Taywee 5y ago
      Unless you're using a shell that subverts that by providing its own built-in, like Zsh, which is allowed because there is no standard for `which`, and depending on its behavior can be problematic and inherently non-portable. That description is also doesn't correctly describe the behavior of the command if the shell has any aliases or built-ins of that name. If you have an alias that points to a different command, then `which` is distinctly not printing the executable that would have been executed.
      - guerrilla 5y ago
        As I said, it depends on which which you mean. In this case, Debian is changing it's behavior away from how it's been for 28 years or whatever and breaking heaps of code and people's habits in the process.
        5y ago
IshKebab 5y ago
> I learned about `command -v` just now reading this article Me too and I'm sure we're not the only ones. But look at this quote from the article: > surely no one competent would choose to have a package depend on `which` when a standard POSIX utility can do a better job This is an mind-bogglingly misguided attitude. Anyone that has never heard of an obscure POSIX command is incompetent? Or is it that really that most people don't want to spend their time writing awful shell scripts and figuring out exactly what is POSIX and what isn't?
- mindcrime 5y ago
  I'd also never heard of `command -v` until reading this article just now. But then I've only been using *nix systems for about 25 years.
- bxparks 5y ago
  I heard of 'command -v' once before years ago, then completely forgot about it until this article. I don't like it because it's harder to type and harder to remember (why the -v?). But I've only been using Unix for 37 years, so I'm not really competent.

by simias 5y ago

guerrilla 5y ago

It's pretty much useless for the same purpose: $ which ls /usr/bin/ls $ type ls ls is aliased to `ls --color=auto' $ command -v ls alias ls='ls --color=auto' Suddenly I find myself irritated at Debian despite not even using it. Why would they not just include the GNU one?

jwmhjwmh 5y ago
I think aliases are only used in interactive shells: $ sh -c 'command -v ls' /bin/ls
scbrg 5y ago
This is a very unlikely output when run from a script using the /bin/sh interpreter on Debian, though. If that is the output you've gone out of your way to create an alias in a script, in which case it's reasonable output. It is what will happen when the script runs that command, after all.
- guerrilla 5y ago
  I'm certain there's masses of code that depends on `which` responding the way it does and scripts with aliases in them regardless of whether that was the right way to do it or not, so your point is probably irrelevant in the grand scheme of things. Think about all that enterprise install and setup crap. People still depend on that spaghetti trash working.
Taywee 5y ago
That depends on whether your shell has a built-in which or not. Mine says % which ls ls: aliased to /bin/ls --color=auto Which makes way more sense. Your "which" is not telling you what will actually be executed when you run the `ls` command there. `command`, on the other hand, is guaranteed to be a built-in, has consistent behavior, and has defined, consistent output, unlike `which`. What `which` outputs will be different depending on shell and what implementation of `which` you actually have installed.
- guerrilla 5y ago
  That depends on which which you mean. Which on GNU has always been this: NAME which - shows the full path of (shell) commands. DESCRIPTION Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been executed when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment vari‐ able PATH using the same algorithm as bash(1).
  - Taywee 5y ago
    Unless you're using a shell that subverts that by providing its own built-in, like Zsh, which is allowed because there is no standard for `which`, and depending on its behavior can be problematic and inherently non-portable. That description is also doesn't correctly describe the behavior of the command if the shell has any aliases or built-ins of that name. If you have an alias that points to a different command, then `which` is distinctly not printing the executable that would have been executed.
    - guerrilla 5y ago
      As I said, it depends on which which you mean. In this case, Debian is changing it's behavior away from how it's been for 28 years or whatever and breaking heaps of code and people's habits in the process.
      - 5y ago

IshKebab 5y ago

> I learned about `command -v` just now reading this article Me too and I'm sure we're not the only ones. But look at this quote from the article: > surely no one competent would choose to have a package depend on `which` when a standard POSIX utility can do a better job This is an mind-bogglingly misguided attitude. Anyone that has never heard of an obscure POSIX command is incompetent? Or is it that really that most people don't want to spend their time writing awful shell scripts and figuring out exactly what is POSIX and what isn't?

mindcrime 5y ago
I'd also never heard of `command -v` until reading this article just now. But then I've only been using *nix systems for about 25 years.
bxparks 5y ago
I heard of 'command -v' once before years ago, then completely forgot about it until this article. I don't like it because it's harder to type and harder to remember (why the -v?). But I've only been using Unix for 37 years, so I'm not really competent.