117

I am trying to create an aliases in bash. What I want to do is map ls -la to ls -la | more

In my .bashrc file this is what I attempted:

alias 'ls -la'='ls -la | more'

However it does not work because (I assume) it has spaces in the alias name. Is there a work around for this?

  • 8
    Why not do alias lsm='ls -la | more' – Nifle Feb 5 '10 at 22:52
126

The Bash documentation states "For almost every purpose, shell functions are preferred over aliases." Here is a shell function that replaces ls and causes output to be piped to more if the argument consists of (only) -la.

ls() {
    if [[ $@ == "-la" ]]; then
        command ls -la | more
    else
        command ls "$@"
    fi
}

As a one-liner:

ls() { if [[ $@ == "-la" ]]; then command ls -la | more; else command ls "$@"; fi; }

Automatically pipe output:

ls -la
  • 1
    why do you need to use double brackets inside the if statement? – sixtyfootersdude Feb 8 '10 at 14:55
  • 1
    @sixtyfootersdude: The double-bracket form is more powerful and I use it by habit. See mywiki.wooledge.org/BashFAQ/031 – Dennis Williamson Feb 8 '10 at 18:35
  • So what is the final command? alias ls='ls()' ?? – Jeef Apr 1 '15 at 12:39
  • 1
    @Jeef: No, my answer uses a function instead of an alias. I have edited it to try to make it clearer. – Dennis Williamson Apr 1 '15 at 14:14
  • 6
    @merlinpatt: command prevents the function from being called recursively. – Dennis Williamson Mar 13 '16 at 18:05
53

From the alias man page:

The first word of each simple command, if unquoted, is checked to see if it has an alias. If so, that word is replaced by the text of the alias. The alias name and the replacement text may contain any valid shell input, including shell metacharacters, with the exception that the alias name may not contain `='.

So, only the first word is checked for alias matches which makes multi-word aliases impossible. You may be able to write a shell script which checks the arguments and calls your command if they match and otherwise just calls the normal ls (See @Dennis Williamson's answer)

  • 8
    +1 For explaining why I am not allowed to use ls -la as an alias. – sixtyfootersdude Feb 8 '10 at 14:49
  • 7
    This was helpful because instead of trying to solve it it answered the question. I came here because i wanted to create an alias with a space in it and that just won't happen. – angryundead Feb 11 '14 at 21:15
  • This not only answered my question, but gave me valuable insight into how the aliasing mechanism actually works. Your quote from the man page was quite helpful. – Lily Finley Jan 21 at 14:32
14

A slightly improved approach taken from Dennis' answer:

function ls() {
  case $* in
    -la* ) shift 1; command ls -la "$@" | more ;;
    * ) command ls "$@" ;;
  esac
}

Or the one-liner:

function ls() { case $* in -la* ) shift 1; command ls -la "$@" | more ;; * ) command ls "$@" ;; esac }

This allows for further options/arguments to be appended after the command if needed, for example ls -la -h

  • 2
    How does this handle if I want ls -lat to be excluded from this treatment? I would need to put a case to handle it above the -la* entry, yes? – Steven Lu Apr 28 '14 at 5:36
-1

You can invoke this alias still, but you need quotation in order that the space is part of the command word. So "ls -la" -p pattern will pass the -p pattern option to more, not ls.

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