alias cs='cd $1; ls'

milanche · 09-12-2005, 11:53 PM

Hi,

I am stuck here, I don't know why this alias doesn't work:

alias cs='cd $1; ls'

When I type cs new_dir, I want to list contents of the new_dir and STAY IN IT. But it always takes me back to the original directory after listing. How can I fix this and, more importantly, WHY doesn't it work?
Thanks for your help.

Emmanuel_uk · 09-13-2005, 02:17 AM

Hi, not sure alias can take parameters like $1

I struggled having something a bit similar to what you are doing.

I eventually defined a function within .bashrc
(cannot remember if I then aliased the function itself)

Am in no way an expert, so add a pinch of salt

scuzzman · 09-13-2005, 05:20 AM

Aliases cannot use arguments as per the above. A better solution would be to write a shell script like so:

Code:

#!/bin/bash

cd $1
ls

#EOF

Use it in the same manner, and call it cs. Make it executable, and stick it in /usr/bin

theYinYeti · 09-13-2005, 06:34 AM

No need to create a script. As said above, in the file where you want to create your alias, create a function instead:

Code:

function cs() {
  cd "$1"; ls
}

You could even refine that a bit, by allowing your function to take parameters for ls:

Code:

function cs() {
  cd "$1"
  shift
  ls "$@"
}

With this function, you could do for example:

Code:

~$ cs some_dir/ -aF
./   gest-fichiers.lib.sh*  logs.sh*    mkAll.sh*  stats.sh*       wlsLinks.sh*
../  ieLinks.sh*            menuV1.sh*  open*      exec.sh*
~/some_dir$

Yves.

archtoad6 · 09-13-2005, 09:35 AM

All good answers, bravo.

The "pecking order" is roughly:[list=1][*]alias[*]function[*]script[/list=1]
Aliases are fast, easy, & hidden; but can't use arguments / parameters.
Functions are fast, easy, & can take arguments / parameters; but aren't hidden -- they clutter the environment.
Scripts can take arguments, do not clutter the environment -- they can be long; but they are:

Not as fast as aliases or functions.
Must have extra lines -- e.g. '#! /bin/bash'.
Must be in separate files.
Must be placed in a directory in the PATH.

In my experience, Debian & MEPIS boxen are notorious for environmental function clutter.
If you want to check your box, run the following 3-part command:

Code:

env|wc ;  set|grep -v "^[[:blank:]{}']\|()\|^$" |wc ;  set|wc

The lines in the output are:[list=1][*]Just the environment variables.[*]All the shell variables stripped of the functions, at least as they are written on my MEPIS 3.3 box.[*]All the shell variables, including the functions.[/list=1] Mine looks like this:

Code:

$ env|wc ;  set|grep -v "^[[:blank:]{}']\|()\|^$" |wc ;  set|wc
     32      36     952
     62      76    1659
   4233   14437  136980

Pretty bloated, eh.

BTW, while we are on the subject, here is one of my favorite functions:

Code:

ll ()
{
    ls -l --color=always $@ | less -RS~#14
}

It takes arguments for ls & sends the output to my favorite pager, preserving the color coding & unfolding long lines.
A good example of what you can learn by R'ingTFM's, ls & less, in this case.

frankie_DJ · 09-13-2005, 02:33 PM

It is NOT TRUE that alias doesn't take positional parametars.
FOr example, I used to have the following alias:

Code:

alias cx='chmod u+x $1'

which I recently replaced with:

Code:

alias cx='chmod u+x $@'

That being said, I too am puzzled as to why milanche's alias doesn't work the way he/she wants it.

slackie1000 · 09-13-2005, 03:04 PM

Quote:

Originally posted by milanche
I want to list contents of the new_dir and STAY IN IT. .... How can I fix this ....

try that..

Code:

alias cs="ls $1 ; cd $1"

i inverted the process but the result is what you want..
regards,
slackie1000

CroMagnon · 09-13-2005, 03:21 PM

Unfortunately, your example doesn't give the results he's after, slackie. It lists the current directory and then changes to the correct one.

aliases definitely do not take parameters, as stated in the man page. Your example and frankie_DJ's example work "by accident". $1 is expanded to nothing when the alias runs, so your alias expands to:
cs thisdir => ls; cd thisdir
(hopefully the bold helps illustrate why your alias appears to work, from a current-directory viewpoint)

frankie's example works the same way.
cx file => chmod u+x file

if you change frankie's alias command to this:
alias cx="chmod u+x $1;"
it will no longer work, because the filename parameter you give it will appear after the semicolon.

archtoad6 · 09-13-2005, 03:30 PM

Thank you CroMagnon. Great counter example adding the ';' just in case they don't believe they were wrong -- it was just an accident that '$1' etc. seemed to work.

frankie_DJ · 09-13-2005, 04:07 PM

CroMagnon, thanks for clearing that up. Quote from man pages:

"...There is no mechanism for using arguments in the replacement text. If arguments are needed, a shell function should be used (see FUNCTIONS below)."

archtoad6 · 09-13-2005, 05:53 PM

I hate being contradicted, esp. when I'm right.

May I take that as an apology?

(One down & one to go ...

)

frankie_DJ · 09-13-2005, 05:57 PM

If you corrected me you would have gotten one.

But you went hiding, untill CroMagnon corrected me.

Still need a big daddy, huh?