I used to use CShell (csh), which lets you make an alias that takes a parameter. The notation was something like
alias junk="mv \\!* ~/.Trash"
In Bash, this does not seem to work. Given that Bash has a multitude of useful features, I would assume that this one has been implemented but I am wondering how.
"$1"
alias test_args="echo PREFIX --$1-- SUFFIX"
, which when called with test_args ABCD
yields the following console output PREFIX ---- SUFFIX ABCD
do
would be impossible or impractical to write as a function. Secondly, for all aliases, you can conveniently expand the alias with A-a
in ZSH or C-A-e
in Bash (or whatever you configure), whereas there is no such functionality available for functions.
Bash alias does not directly accept parameters. You will have to create a function.
alias
does not accept parameters but a function can be called just like an alias. For example:
myfunction() {
#do things with parameters like $1 such as
mv "$1" "$1.bak"
cp "$2" "$1"
}
myfunction old.conf new.conf #calls `myfunction`
By the way, Bash functions defined in your .bashrc
and other files are available as commands within your shell. So for instance you can call the earlier function like this
$ myfunction original.conf my.conf
Refining the answer above, you can get 1-line syntax like you can for aliases, which is more convenient for ad-hoc definitions in a shell or .bashrc files:
bash$ myfunction() { mv "$1" "$1.bak" && cp -i "$2" "$1"; }
bash$ myfunction original.conf my.conf
Don't forget the semi-colon before the closing right-bracket. Similarly, for the actual question:
csh% alias junk="mv \\!* ~/.Trash"
bash$ junk() { mv "$@" ~/.Trash/; }
Or:
bash$ junk() { for item in "$@" ; do echo "Trashing: $item" ; mv "$item" ~/.Trash/; done; }
mv "$1" "$1.bak"; cp "$2" "$1"
into mv "$1" "$1.bak" && cp "$2" "$1"
to not lose your data when mv
runs into trouble (e.g., file system full).
The question is simply asked wrong. You don't make an alias that takes parameters because alias
just adds a second name for something that already exists. The functionality the OP wants is the function
command to create a new function. You do not need to alias the function as the function already has a name.
I think you want something like this :
function trash() { mv "$@" ~/.Trash; }
That's it! You can use parameters $1, $2, $3, etc, or just stuff them all with $@
echo -e '#!/bin/bash\nshopt -s expand_aliases\nalias asrc='\''echo "${BASH_SOURCE[0]}"'\'' # note the '\''s\nfunction fsrc(){ echo "${BASH_SOURCE[0]}";}'>>file2&&echo -e '#!/bin/bash\n. file2\nalias rl='\''readlink -f'\''\nrl $(asrc)\nrl $(fsrc)'>>file1&&chmod +x file1&&./file1;rm -f file1 file2
$@
to support file names with spaces, etc.
TL;DR: Do this instead
Its far easier and more readable to use a function than an alias to put arguments in the middle of a command.
$ wrap_args() { echo "before $@ after"; }
$ wrap_args 1 2 3
before 1 2 3 after
If you read on, you'll learn things that you don't need to know about shell argument processing. Knowledge is dangerous. Just get the outcome you want, before the dark side forever controls your destiny.
Clarification
bash
aliases do accept arguments, but only at the end:
$ alias speak=echo
$ speak hello world
hello world
Putting arguments into the middle of command via alias
is indeed possible but it gets ugly.
Don't try this at home, kiddies!
If you like circumventing limitations and doing what others say is impossible, here's the recipe. Just don't blame me if your hair gets frazzled and your face ends up covered in soot mad-scientist-style.
The workaround is to pass the arguments that alias
accepts only at the end to a wrapper that will insert them in the middle and then execute your command.
Solution 1
If you're really against using a function per se, you can use:
$ alias wrap_args='f(){ echo before "$@" after; unset -f f; }; f'
$ wrap_args x y z
before x y z after
You can replace $@
with $1
if you only want the first argument.
Explanation 1
This creates a temporary function f
, which is passed the arguments (note that f
is called at the very end). The unset -f
removes the function definition as the alias is executed so it doesn't hang around afterwards.
Solution 2
You can also use a subshell:
$ alias wrap_args='sh -c '\''echo before "$@" after'\'' _'
Explanation 2
The alias builds a command like:
sh -c 'echo before "$@" after' _
Comments:
The placeholder _ is required, but it could be anything. It gets set to sh's $0, and is required so that the first of the user-given arguments don't get consumed. Demonstration: sh -c 'echo Consumed: "$0" Printing: "$@"' alcohol drunken babble Consumed: alcohol Printing: drunken babble
The single-quotes inside single-quotes are required. Here's an example of it not working with double quotes: $ sh -c "echo Consumed: $0 Printing: $@" alcohol drunken babble Consumed: -bash Printing: Here the values of the interactive shell's $0 and $@ are replaced into the double quoted before it is passed to sh. Here's proof: echo "Consumed: $0 Printing: $@" Consumed: -bash Printing: The single quotes ensure that these variables are not interpreted by interactive shell, and are passed literally to sh -c. You could use double-quotes and \$@, but best practice is to quote your arguments (as they may contain spaces), and \"\$@\" looks even uglier, but may help you win an obfuscation contest where frazzled hair is a prerequisite for entry.
alias gc='git checkout'
$@
? They are necessary if you have, eg, files with spaces in them.
\df
All you have to do is make a function inside an alias:
$ alias mkcd='_mkcd(){ mkdir "$1"; cd "$1";}; _mkcd'
^ * ^ ^ ^ ^ ^
You must put double quotes around "$1" because single quotes will not work. This is because clashing the quotes at the places marked with arrows confuses the system. Also, a space at the place marked with a star is needed for the function.
bash: syntax error near unexpected token '{mkdir'
.
function
prefix, see discussion in wiki.bash-hackers.org/scripting/obsolete. That said, I don't know why anyone would do this in preference to only defining a function and not using any alias at all.
command
. you could even use an alias like alias c = 'command'
and then simply use c ls
.
An alternative solution is to use marker, a tool I've created recently that allows you to "bookmark" command templates and easily place cursor at command place-holders:
https://i.stack.imgur.com/0fyiS.gif
I found that most of time, I'm using shell functions so I don't have to write frequently used commands again and again in the command-line. The issue of using functions for this use case, is adding new terms to my command vocabulary and having to remember what functions parameters refer to in the real-command. Marker goal is to eliminate that mental burden.
Once i did some fun project and i still use it. It's showing some animation while i copy files via cp
command coz cp
don't show anything and it's kind of frustrating. So i made this alias
alias cp="~/SCR/spiner cp"
And this is the spiner script
#!/bin/bash
#Set timer
T=$(date +%s)
#Add some color
. ~/SCR/color
#Animation sprites
sprite=( "(* ) ( *)" " (* )( *) " " ( *)(* ) " "( *) (* )" "(* ) ( *)" )
#Print empty line and hide cursor
printf "\n${COF}"
#Exit function
function bye { printf "${CON}"; [ -e /proc/$pid ] && kill -9 $pid; exit; }; trap bye INT
#Run our command and get its pid
"$@" & pid=$!
#Waiting animation
i=0; while [ -e /proc/$pid ]; do sleep 0.1
printf "\r${GRN}Please wait... ${YLW}${sprite[$i]}${DEF}"
((i++)); [[ $i = ${#sprite[@]} ]] && i=0
done
#Print time and exit
T=$(($(date +%s)-$T))
printf "\n\nTime taken: $(date -u -d @${T} +'%T')\n"
bye
It's look like this
https://i.stack.imgur.com/e3DAc.gif
Cycled animation)
https://i.stack.imgur.com/kTUMZ.gif
Here is the link to a color script mentioned above. And new animation cycle)
https://i.stack.imgur.com/ifc5n.gif
Syntax:
alias shortName="your custom command here"
Example:
alias tlogs='_t_logs() { tail -f ../path/$1/to/project/logs.txt ;}; _t_logs'
>
prompt, make sure you got the ;
before the }
. Also note this redefines the function every time you use the alias, so if the function definition is expensive, it could be better to move it out of the alias
.
alias kj='_kc_jq() { kc get -o json $@ |jq; }; _kc_jq'
Bash alias absolutely does accept parameters. I just added an alias to create a new react app which accepts the app name as a parameter. Here's my process:
Open the bash_profile for editing in nano
nano /.bash_profile
Add your aliases, one per line:
alias gita='git add .'
alias gitc='git commit -m "$@"'
alias gitpom='git push origin master'
alias creact='npx create-react-app "$@"'
note: the "$@" accepts parameters passed in like "creact my-new-app"
Save and exit nano editor
ctrl+o to to write (hit enter); ctrl+x to exit
Tell terminal to use the new aliases in .bash_profile
source /.bash_profile
That's it! You can now use your new aliases
gitc foo
runs git commit -m foo
not because you have a $@ but because foo came at the end -- it's running git commit -m
and you happened to have a foo
that followed and was appended and that made your command valid.
$@
in an alias def.
set -- "first argument" "second argument"
before calling your aliases, all the "$@"
s will turn into "first argument" "second argument"
s. They don't reflect the parameters passed to your alias; they only reflect the parameters that are active inside the context in which the alias is called.
Here's are three examples of functions I have in my ~/.bashrc
, that are essentially aliases that accept a parameter:
#Utility required by all below functions.
#https://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-bash-variable#comment21953456_3232433
alias trim="sed -e 's/^[[:space:]]*//g' -e 's/[[:space:]]*\$//g'"
.
:<<COMMENT
Alias function for recursive deletion, with are-you-sure prompt.
Example:
srf /home/myusername/django_files/rest_tutorial/rest_venv/
Parameter is required, and must be at least one non-whitespace character.
Short description: Stored in SRF_DESC
With the following setting, this is *not* added to the history:
export HISTIGNORE="*rm -r*:srf *"
- https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
See:
- y/n prompt: https://stackoverflow.com/a/3232082/2736496
- Alias w/param: https://stackoverflow.com/a/7131683/2736496
COMMENT
#SRF_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
SRF_DESC="srf [path]: Recursive deletion, with y/n prompt\n"
srf() {
#Exit if no parameter is provided (if it's the empty string)
param=$(echo "$1" | trim)
echo "$param"
if [ -z "$param" ] #http://tldp.org/LDP/abs/html/comparison-ops.html
then
echo "Required parameter missing. Cancelled"; return
fi
#Actual line-breaks required in order to expand the variable.
#- https://stackoverflow.com/a/4296147/2736496
read -r -p "About to
sudo rm -rf \"$param\"
Are you sure? [y/N] " response
response=${response,,} # tolower
if [[ $response =~ ^(yes|y)$ ]]
then
sudo rm -rf "$param"
else
echo "Cancelled."
fi
}
.
:<<COMMENT
Delete item from history based on its line number. No prompt.
Short description: Stored in HX_DESC
Examples
hx 112
hx 3
See:
- https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
COMMENT
#HX_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
HX_DESC="hx [linenum]: Delete history item at line number\n"
hx() {
history -d "$1"
}
.
:<<COMMENT
Deletes all lines from the history that match a search string, with a
prompt. The history file is then reloaded into memory.
Short description: Stored in HXF_DESC
Examples
hxf "rm -rf"
hxf ^source
Parameter is required, and must be at least one non-whitespace character.
With the following setting, this is *not* added to the history:
export HISTIGNORE="*hxf *"
- https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
See:
- https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
COMMENT
#HXF_DESC: For "aliaf" command (with an 'f'). Must end with a newline.
HXF_DESC="hxf [searchterm]: Delete all history items matching search term, with y/n prompt\n"
hxf() {
#Exit if no parameter is provided (if it's the empty string)
param=$(echo "$1" | trim)
echo "$param"
if [ -z "$param" ] #http://tldp.org/LDP/abs/html/comparison-ops.html
then
echo "Required parameter missing. Cancelled"; return
fi
read -r -p "About to delete all items from history that match \"$param\". Are you sure? [y/N] " response
response=${response,,} # tolower
if [[ $response =~ ^(yes|y)$ ]]
then
#Delete all matched items from the file, and duplicate it to a temp
#location.
grep -v "$param" "$HISTFILE" > /tmp/history
#Clear all items in the current sessions history (in memory). This
#empties out $HISTFILE.
history -c
#Overwrite the actual history file with the temp one.
mv /tmp/history "$HISTFILE"
#Now reload it.
history -r "$HISTFILE" #Alternative: exec bash
else
echo "Cancelled."
fi
}
References:
Trimming whitespace from strings: How to trim whitespace from a Bash variable?
Actual line breaks: https://stackoverflow.com/a/4296147/2736496
Alias w/param: https://stackoverflow.com/a/7131683/2736496 (another answer in this question)
HISTIGNORE: https://superuser.com/questions/232885/can-you-share-wisdom-on-using-histignore-in-bash
Y/N prompt: https://stackoverflow.com/a/3232082/2736496
Delete all matching items from history: https://unix.stackexchange.com/questions/57924/how-to-delete-commands-in-history-matching-a-given-string
Is string null/empty: http://tldp.org/LDP/abs/html/comparison-ops.html
Respectfully to all those saying you can't insert a parameter in the middle of an alias I just tested it and found that it did work.
alias mycommand = "python3 "$1" script.py --folderoutput RESULTS/"
when I then ran mycommand foobar it worked exactly as if I had typed the command out longhand.
alias myalias="echo 1 "$1" 3"; myalias 2
gives me: 1 3 2
alias mycommand = "python3 script.py --folderoutput RESULTS/"
(with omitting "$1"
). It's the same because alias does not set positional parameters in bash. In an interactive shell, their value is "" an empty string, unless you put something in there. To further test that, try really adding something to $1: set -- something
before defining alias. now your alias is very possibly broken, see what that alias contains: alias mycommand
$1
gets substituted with empty string and your comment gets appended. You can safely redefine your alias to git commit -m
and it will still work.
If you're looking for a generic way to apply all params to a function, not just one or two or some other hardcoded amount, you can do that this way:
#!/usr/bin/env bash
# you would want to `source` this file, maybe in your .bash_profile?
function runjar_fn(){
java -jar myjar.jar "$@";
}
alias runjar=runjar_fn;
So in the example above, i pass all parameters from when i run runjar
to the alias.
For example, if i did runjar hi there
it would end up actually running java -jar myjar.jar hi there
. If i did runjar one two three
it would run java -jar myjar.jar one two three
.
I like this $@
- based solution because it works with any number of params.
runjar
instead of making it an alias to a function? Seems needlessly complicated!
alias
-ed (or having the properties of things passed to alias
) in bash files? if yes, then its just my not having known that
alias runjar='java -jar myjar.jar'
. Aliases do accept arguments, but only at the end.
NB: In case the idea isn't obvious, it is a bad idea to use aliases for anything but aliases, the first one being the 'function in an alias' and the second one being the 'hard to read redirect/source'. Also, there are flaws (which i thought would be obvious, but just in case you are confused: I do not mean them to actually be used... anywhere!)
................................................................................................................................................
I've answered this before, and it has always been like this in the past:
alias foo='__foo() { unset -f $0; echo "arg1 for foo=$1"; }; __foo()'
which is fine and good, unless you are avoiding the use of functions all together. in which case you can take advantage of bash's vast ability to redirect text:
alias bar='cat <<< '\''echo arg1 for bar=$1'\'' | source /dev/stdin'
They are both about the same length give or take a few characters.
The real kicker is the time difference, the top being the 'function method' and the bottom being the 'redirect-source' method. To prove this theory, the timing speaks for itself:
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.004s sys 0m0.008s # <--time spent in foo
real 0m0.000s user 0m0.000s sys 0m0.000s # <--time spent in bar
arg1 for bar=BARVALUE
ubuntu@localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu@localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.000s sys 0m0.012s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu@localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.012s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu@localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.008s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
This is the bottom part of about 200 results, done at random intervals. It seems that function creation/destruction takes more time than redirection. Hopefully this will help future visitors to this question (didn't want to keep it to myself).
time for i in {1..1000}; do foo FOOVALUE; done
→ 0m0.028s. But time for i in {1..1000}; do bar FOOVALUE; done
→ 0m2.739s. Bar is two orders of magnitude slower than foo. Just using a plain function instead of an alias reduces runtime by another 30%: function boo() { echo "arg1 for boo=$1" ; }
⇒ time for i in {1..1000}; do boo FOOVALUE; done
→ 0m0.019s.
I will just post my (hopefully, okay) solution (for future readers, & most vitally; editors). So - please edit & improve/remove anything in this post.
In the terminal:
$ alias <name_of_your_alias>_$argname="<command> $argname"
and to use it (notice the space after '_':
$<name_of_your_alias>_ $argname
for example, a alias to cat
a file called hello.txt
:
(alias name is CAT_FILE_)
and the $f (is the $argname, which is a file in this example)
$ alias CAT_FILE_$f="cat $f"
$ echo " " >> hello.txt
$ echo "hello there!" >> hello.txt
$ echo " " >> hello.txt
$ cat hello.txt
hello there!
Test (notice the space after '_'):
CAT_FILE_ hello.txt
$f
is at the end. The $f
is probably empty at alias definition time and therefore resolves into alias CAT_FILE_="cat "
. Just run alias
to see the resulting definition. So when you call CAT_FILE_
you just pass the argument to the alias as in any other alias usage like in alias ll="ls -l"
. Try to put the "argument" $f
somewhere else than at the end and this won't work. E.g: alias ECHO_ARG_$f="echo xxx $f yyy"
. Then ECHO_ARG_ test
leads to xxx yyy test
.
There are legitimate technical reasons to want a generalized solution to the problem of bash alias not having a mechanism to take a reposition arbitrary arguments. One reason is if the command you wish to execute would be adversely affected by the changes to the environment that result from executing a function. In all other cases, functions should be used.
What recently compelled me to attempt a solution to this is that I wanted to create some abbreviated commands for printing the definitions of variables and functions. So I wrote some functions for that purpose. However, there are certain variables which are (or may be) changed by a function call itself. Among them are:
FUNCNAME BASH_SOURCE BASH_LINENO BASH_ARGC BASH_ARGV
The basic command I had been using (in a function) to print variable defns. in the form output by the set command was:
sv () { set | grep --color=never -- "^$1=.*"; }
E.g.:
> V=voodoo
sv V
V=voodoo
Problem: This won't print the definitions of the variables mentioned above as they are in the current context, e.g., if in an interactive shell prompt (or not in any function calls), FUNCNAME isn't defined. But my function tells me the wrong information:
> sv FUNCNAME
FUNCNAME=([0]="sv")
One solution I came up with has been mentioned by others in other posts on this topic. For this specific command to print variable defns., and which requires only one argument, I did this:
alias asv='(grep -- "^$(cat -)=.*" <(set)) <<<'
Which gives the correct output (none), and result status (false):
> asv FUNCNAME
> echo $?
1
However, I still felt compelled to find a solution that works for arbitrary numbers of arguments.
A General Solution To Passing Arbitrary Arguments To A Bash Aliased Command:
# (I put this code in a file "alias-arg.sh"):
# cmd [arg1 ...] – an experimental command that optionally takes args,
# which are printed as "cmd(arg1 ...)"
#
# Also sets global variable "CMD_DONE" to "true".
#
cmd () { echo "cmd($@)"; declare -g CMD_DONE=true; }
# Now set up an alias "ac2" that passes to cmd two arguments placed
# after the alias, but passes them to cmd with their order reversed:
#
# ac2 cmd_arg2 cmd_arg1 – calls "cmd" as: "cmd cmd_arg1 cmd_arg2"
#
alias ac2='
# Set up cmd to be execed after f() finishes:
#
trap '\''cmd "${CMD_ARGV[1]}" "${CMD_ARGV[0]}"'\'' SIGUSR1;
# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# (^This is the actually execed command^)
#
# f [arg0 arg1 ...] – acquires args and sets up trap to run cmd:
f () {
declare -ag CMD_ARGV=("$@"); # array to give args to cmd
kill -SIGUSR1 $$; # this causes cmd to be run
trap SIGUSR1; # unset the trap for SIGUSR1
unset CMD_ARGV; # clean up env...
unset f; # incl. this function!
};
f' # Finally, exec f, which will receive the args following "ac2".
E.g.:
> . alias-arg.sh
> ac2 one two
cmd(two one)
>
> # Check to see that command run via trap affects this environment:
> asv CMD_DONE
CMD_DONE=true
A nice thing about this solution is that all the special tricks used to handle positional parameters (arguments) to commands will work when composing the trapped command. The only difference is that array syntax must be used.
E.g.,
If you want "$@", use "${CMD_ARGV[@]}".
If you want "$#", use "${#CMD_ARGV[@]}".
Etc.
As has already been pointed out by others, using a function should be considered best practice.
However, here is another approach, leveraging xargs
:
alias junk="xargs -I "{}" -- mv "{}" "~/.Trash" <<< "
Note that this has side effects regarding redirection of streams.
alias junk=xargs -I \"{}\" -- mv \"{}\" \"~/.Trash\" <<<"
).
xargs
isn't doing textual substitution (it operates on the array of C strings generated after shell parsing is already over, so quotes no longer have value wrt changing shell behavior), and when quoted ~
doesn't work. So this would be better as just alias junk='xargs -I {} -- mv {} ~/.Trash <<<'
Here's the example:
alias gcommit='function _f() { git add -A; git commit -m "$1"; } ; _f'
Very important:
There is a space after { and before }. There is a ; after each command in sequence. If you forget this after the last command, you will see > prompt instead! The argument is enclosed in quotes as "$1"
To give specific answer to the Question posed about creating the alias to move the files to Trash folder instead of deleting them:
alias rm="mv "$1" -t ~/.Trash/"
Offcourse you have to create dir ~/.Trash first.
Then just give following command:
$rm <filename>
$rm <dirname>
alias rm="mv "$i_bellieve_this_is_correct_because_it_WORKS" -t ~/.Trash/"
Who is still not convinced can run this command before: set -- my_very_important_file
Run it literally or use path to your very important file if you feel confident $1 in alias works. now statement: alias rm="mv "$1" -t ~/.Trash/"
and rm <filename>
as suggested. set --
sets value to positional parameter $1. alias command does not.
$1
is completely empty, mv
still honors arguments in trailing position. The $1
is not populated by the arguments passed to your alias; it's populated from the $1
value that was preexisting in the shell in which the alias was run.
Solution with subcommands:
d () {
if [ $# -eq 0 ] ; then
docker
return 0
fi
CMD=$1
shift
case $CMD in
p)
docker ps --all $@
;;
r)
docker run --interactive --tty $@
;;
rma)
docker container prune
docker image prune --filter "dangling=true"
;;
*)
docker $CMD $@
;;
esac
return $?
}
Using:
$ d r my_image ...
Called:
docker run --interactive --tty my_image ...
Functions are indeed almost always the answer as already amply contributed and confirmed by this quote from the man page: "For almost every purpose, aliases are superseded by shell functions."
For completeness and because this can be useful (marginally more lightweight syntax) it could be noted that when the parameter(s) follow the alias, they can still be used (although this wouldn't address the OP's requirement). This is probably easiest to demonstrate with an example:
alias ssh_disc='ssh -O stop'
allows me to type smth like ssh_disc myhost
, which gets expanded as expected as: ssh -O stop myhost
This can be useful for commands which take complex arguments (my memory isn't what it use t be anymore...)
For taking parameters, you should use functions!
However $@ get interpreted when creating the alias instead of during the execution of the alias and escaping the $ doesn’t work either. How do I solve this problem?
You need to use shell function instead of an alias to get rid of this problem. You can define foo as follows:
function foo() { /path/to/command "$@" ;}
OR
foo() { /path/to/command "$@" ;}
Finally, call your foo() using the following syntax:
foo arg1 arg2 argN
Make sure you add your foo() to ~/.bash_profile
or ~/.zshrc
file.
In your case, this will work
function trash() { mv $@ ~/.Trash; }
Both functions and aliases can use parameters as others have shown here. Additionally, I would like to point out a couple of other aspects:
1. function runs in its own scope, alias shares scope
It may be useful to know this difference in cases you need to hide or expose something. It also suggests that a function is the better choice for encapsulation.
function tfunc(){
GlobalFromFunc="Global From Func" # Function set global variable by default
local FromFunc="onetwothree from func" # Set a local variable
}
alias talias='local LocalFromAlias="Local from Alias"; GlobalFromAlias="Global From Alias" # Cant hide a variable with local here '
# Test variables set by tfunc
tfunc # call tfunc
echo $GlobalFromFunc # This is visible
echo $LocalFromFunc # This is not visible
# Test variables set by talias
# call talias
talias
echo $GlobalFromAlias # This is invisible
echo $LocalFromAlias # This variable is unset and unusable
Output:
bash-3.2$ # Test variables set by tfunc
bash-3.2$ tfunc # call tfunc
bash-3.2$ echo $GlobalFromFunc # This is visible
Global From Func
bash-3.2$ echo $LocalFromFunc # This is not visible
bash-3.2$ # Test variables set by talias
bash-3.2$ # call talias
bash-3.2$ talias
bash: local: can only be used in a function
bash-3.2$ echo $GlobalFromAlias # This is invisible
Global From Alias
bash-3.2$ echo $LocalFromAlias # This variable is unset and unusable
2. wrapper script is a better choice
It has happened to me several times that an alias or function can not be found when logging in via ssh
or involving switching usernames or multi-user environment. There are tips and tricks with sourcing dot files, or this interesting one with alias: alias sd='sudo '
lets this subsequent alias alias install='sd apt-get install'
work as expect (notice the extra space in sd='sudo '
). However, a wrapper script works better than a function or alias in cases like this. The main advantage with a wrapper script is that it is visible/executable for under intended path (i.e. /usr/loca/bin/) where as a function/alias needs to be sourced before it is usable. For example, you put a function in a ~/.bash_profile or ~/.bashrc for bash
, but later switch to another shell (i.e. zsh
) then the function is not visible anymore. So, when you are in doubt, a wrapper script is always the most reliable and portable solution.
source
in a function works just fine.
f () { source /tmp/nst; }
does exactly what I expect. Maybe your PATH
is wrong so it runs the wrong activate
or something; but running source
from a function works fine.
function
keyword in your definition, see wiki.bash-hackers.org/scripting/obsolete -- function funcname {
is ancient ksh syntax bash supports for backwards compatibility with pre-POSIX shells, whereas funcname() {
is official POSIX-standardized syntax. function funcname() {
is a mismash of the two that isn't compatible with ancient ksh or compatible with POSIX sh, and which thus is best avoided.
Here is another approach using read
. I am using this for brute search of a file by its name fragment, ignoring the "permission denied" messages.
alias loc0='{ IFS= read -r x; find . -iname "*" -print 2>/dev/null | grep $x;} <<<'
A simple example:
$ { IFS= read -r x; echo "1 $x 2 ";} <<< "a b"
1 a b 2
Note, that this converts the argument as a string into variable(s). One could use several parameters within quotes for this, space separated:
$ { read -r x0 x1; echo "1 ${x0} 2 ${x1} 3 ";} <<< "a b"
1 a 2 b 3
alias junk="delay-arguments mv _ ~/.Trash"
delay-arguments
script:
#!/bin/bash
# Example:
# > delay-arguments echo 1 _ 3 4 2
# 1 2 3 4
# > delay-arguments echo "| o n e" _ "| t h r e e" "| f o u r" "| t w o"
# | o n e | t w o | t h r e e | f o u r
RAW_ARGS=("$@")
ARGS=()
ARG_DELAY_MARKER="_"
SKIPPED_ARGS=0
SKIPPED_ARG_NUM=0
RAW_ARGS_COUNT="$#"
for ARG in "$@"; do
#echo $ARG
if [[ "$ARG" == "$ARG_DELAY_MARKER" ]]; then
SKIPPED_ARGS=$((SKIPPED_ARGS+1))
fi
done
for ((I=0; I<$RAW_ARGS_COUNT-$SKIPPED_ARGS; I++)); do
ARG="${RAW_ARGS[$I]}"
if [[ "$ARG" == "$ARG_DELAY_MARKER" ]]; then
MOVE_SOURCE_ARG_NUM=$(($RAW_ARGS_COUNT-$SKIPPED_ARGS+$SKIPPED_ARG_NUM))
MOVING_ARG="${RAW_ARGS[$MOVE_SOURCE_ARG_NUM]}"
if [[ "$MOVING_ARG" == "$ARG_DELAY_MARKER" ]]; then
echo "Error: Not enough arguments!"
exit 1;
fi
#echo "Moving arg: $MOVING_ARG"
ARGS+=("$MOVING_ARG")
SKIPPED_ARG_NUM=$(($SKIPPED_ARG_NUM+1))
else
ARGS+=("$ARG")
fi
done
#for ARG in "${ARGS[@]}"; do
#echo "ARGN: $ARG"
#done
#echo "RAW_ARGS_COUNT: $RAW_ARGS_COUNT"
#echo "SKIPPED_ARGS: $SKIPPED_ARGS"
#echo "${ARGS[@]}"
QUOTED_ARGS=$(printf ' %q' "${ARGS[@]}")
eval "${QUOTED_ARGS[@]}"
mv
has a -t
option which solves this for that particular command in a different way.)
Success story sharing
$1
in quotes?source
ing your .bashrc will add the function but it won't unalias the old alias. Since aliases are higher precedent than functions, it will try to use the alias. You need to either close and reopen your shell, or else callunalias <name>
. Perhaps I'll save someone the 5 minutes I just wasted.exec bash
: It will start a new shell, giving you a clean read of your configs, just as if you closed and reopened, but keeping that session's environment variable settings too. Also, executingbash
without the exec can be useful when you want to handle thinks like a stack.mv "$1" "$1.bak"
. without quotes, if $1 were "hello world", you would executemv hello world hello world.bak
instead ofmv "hello world" "hello world.bak"
.