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.
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; }
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 $#
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.
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 "$1" because single quotes will not work. This is because clashing the quotes at the places marked with arrows confuses the system. Also, a space at the place marked with a star is needed for the function.
Once I did some fun project and I'm still using it. It's showing some animation while copy files via cp command coz cp don't show anything and it's kind of frustrating. So I've made this alias for cp:
alias cp="~/SCR/spinner cp"
And this is the spinner script
#!/bin/bash
#Set timer
T=$(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 looks like this
Cycled animation)
Here is the link to a color script mentioned above.
And new animation cycle)
So the answer to the OP's question is to use intermediate script that could shuffle args as you wish.
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:
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.
Syntax:
alias shortName="your custom command here"
Example:
alias tlogs='_t_logs() { tail -f ../path/$1/to/project/logs.txt ;}; _t_logs'
Bash alias absolutely does accept parameters. I just added an alias to create a new react app which accepts the app name as a parameter. Here's my process:
Open the bash_profile for editing in nano
nano /.bash_profile
Add your aliases, one per line:
alias gita='git add .'
alias gitc='git commit -m "$#"'
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
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.
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=$1'\'' | source /dev/stdin'
They are both about the same length give or take a few characters.
The real kicker is the time difference, the top being the 'function method' and the bottom being the 'redirect-source' method. To prove this theory, the timing speaks for itself:
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.004s sys 0m0.008s # <--time spent in foo
real 0m0.000s user 0m0.000s sys 0m0.000s # <--time spent in bar
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.011s user 0m0.000s sys 0m0.012s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.012s user 0m0.004s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
ubuntu#localhost /usr/bin# time foo FOOVALUE; time bar BARVALUE
arg1 for foo=FOOVALUE
real 0m0.010s user 0m0.008s sys 0m0.004s
real 0m0.000s user 0m0.000s sys 0m0.000s
arg1 for bar=BARVALUE
This is the bottom part of about 200 results, done at random intervals. It seems that function creation/destruction takes more time than redirection. Hopefully this will help future visitors to this question (didn't want to keep it to myself).
If you're looking for a generic way to apply all params to a function, not just one or two or some other hardcoded amount, you can do that this way:
#!/usr/bin/env bash
# you would want to `source` this file, maybe in your .bash_profile?
function runjar_fn(){
java -jar myjar.jar "$#";
}
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.
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.
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
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.
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 ...
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>
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
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.
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[#]}"
Let's assume I have 3 shell scripts:
script_1.sh
#!/bin/bash
./script_3.sh
script_2.sh
#!/bin/bash
./script_3.sh
the problem is that in script_3.sh I want to know the name of the caller script.
so that I can respond differently to each caller I support
please don't assume I'm asking about $0 cause $0 will echo script_3 every time no matter who is the caller
here is an example input with expected output
./script_1.sh should echo script_1
./script_2.sh should echo script_2
./script_3.sh should echo user_name or root or anything to distinguish between the 3 cases?
Is that possible? and if possible, how can it be done?
this is going to be added to a rm modified script... so when I call rm it do something and when git or any other CLI tool use rm it is not affected by the modification
Based on #user3100381's answer, here's a much simpler command to get the same thing which I believe should be fairly portable:
PARENT_COMMAND=$(ps -o comm= $PPID)
Replace comm= with args= to get the full command line (command + arguments). The = alone is used to suppress the headers.
See: http://pubs.opengroup.org/onlinepubs/009604499/utilities/ps.html
In case you are sourceing instead of calling/executing the script there is no new process forked and thus the solutions with ps won't work reliably.
Use bash built-in caller in that case.
$ cat h.sh
#! /bin/bash
function warn_me() {
echo "$#"
caller
}
$
$ cat g.sh
#!/bin/bash
source h.sh
warn_me "Error: You did not do something"
$
$ . g.sh
Error: You did not do something
g.sh
$
Source
The $PPID variable holds the parent process ID. So you could parse the output from ps to get the command.
#!/bin/bash
PARENT_COMMAND=$(ps $PPID | tail -n 1 | awk "{print \$5}")
Based on #J.L.answer, with more in depth explanations, that works for linux :
cat /proc/$PPID/comm
gives you the name of the command of the parent pid
If you prefer the command with all options, then :
cat /proc/$PPID/cmdline
explanations :
$PPID is defined by the shell, it's the pid of the parent processes
in /proc/, you have some dirs with the pid of each process (linux). Then, if you cat /proc/$PPID/comm, you echo the command name of the PID
Check man proc
Couple of useful files things kept in /proc/$PPID here
/proc/*some_process_id*/exe A symlink to the last executed command under *some_process_id*
/proc/*some_process_id*/cmdline A file containing the last executed command under *some_process_id* and null-byte separated arguments
So a slight simplification.
sed 's/\x0/ /g' "/proc/$PPID/cmdline"
If you have /proc:
$(cat /proc/$PPID/comm)
Declare this:
PARENT_NAME=`ps -ocomm --no-header $PPID`
Thus you'll get a nice variable $PARENT_NAME that holds the parent's name.
You can simply use the command below to avoid calling cut/awk/sed:
ps --no-headers -o command $PPID
If you only want the parent and none of the subsequent processes, you can use:
ps --no-headers -o command $PPID | cut -d' ' -f1
You could pass in a variable to script_3.sh to determine how to respond...
script_1.sh
#!/bin/bash
./script_3.sh script1
script_2.sh
#!/bin/bash
./script_3.sh script2
script_3.sh
#!/bin/bash
if [ $1 == 'script1' ] ; then
echo "we were called from script1!"
elsif [ $1 == 'script2' ] ; then
echo "we were called from script2!"
fi
Recently I have been reading The Advanced Bash Script and I find something about the variable scope between parent and children shells puzzle me so much. Here it is:
Scene:
there are some ways to spawn a child shell:
first, (command-lists);
second, execute a non-built-in command or a script, and so on.
Since when we run a script in the parent script, the child script can not see the variables in the parent shell. Why is it possible that in the (command-lists) struct the child shell can seen the variable in the parent shell.
e.g
(command-lists)
$ a=100
$ (echo $a)
100
$
run a script
$ cat b.sh
echo $a
$ a=100
$ ./b.sh
# empty
How?
In the case where you have a sub-shell run in the original script:
(command1; command2; ...)
the sub-shell is a direct copy of the original shell created by fork(), and therefore has direct access to its own copy of all the original variables available to it.
Suppose the commands (command1, command2 etc) in the sub-shell are themselves shell scripts. Those commands are executed by the sub-shell calling fork() and then exec() to create a new shell, and the new shell does not inherit the non-exported variables from the original shell.
Addressing your examples directly:
$ a=100
$ (echo $a)
100
$
Here, the sub-shell has its own copy of all the variables (specifically, a) that the parent shell had access to. Any changes made in the sub-shell will not be reflected in the parent shell, of course, so:
$ a=100
$ (echo $a; a=200; echo $a)
100
200
$ echo $a
100
$
Now your second example:
$ cat b.sh
echo $a
$ a=100
$ ./b.sh
$ . ./b.sh
100
$ source ./b.sh
100
$ a=200 ./b.sh
200
$ echo $a
100
$ export a
$ ./b.sh
100
$
The variable a is not exported, so the first time b.sh is run, it has no value for $a so it echoes an empty line. The second two examples are a 'cheat'; the shell reads the script b.sh as if it was part of the current shell (no fork()) so the variables are still accessible to b.sh, hence it echoes 100 each time. (Dot or . is the older mechanism for reading a script in the current shell; the Bourne shell in 7th Edition UNIX used it. The source command is borrowed from the C shells as an equivalent mechanism.)
The command a=200 ./b.sh exports a for the duration of the command, so b.sh sees and echoes the modified value 200 but the main shell has a unchanged. Then when a is exported, it is available to b.sh automatically, hence it sees and echoes the last 100.
When using a *nix shell (usually bash), I often spawn a sub-shell with which I can take care of a small task (usually in another directory), then exit out of to resume the session of the parent shell.
Once in a while, I'll lose track of whether I'm running a nested shell, or in my top-level shell, and I'll accidentally spawn an additional sub-shell or exit out of the top-level shell by mistake.
Is there a simple way to determine whether I'm running in a nested shell? Or am I going about my problem (by spawning sub-shells) in a completely wrong way?
The $SHLVL variable tracks your shell nesting level:
$ echo $SHLVL
1
$ bash
$ echo $SHLVL
2
$ exit
$ echo $SHLVL
1
As an alternative to spawning sub-shells you could push and pop directories from the stack and stay in the same shell:
[root#localhost /old/dir]# pushd /new/dir
/new/dir /old/dir
[root#localhost /new/dir]# popd
/old/dir
[root#localhost /old/dir]#
Here is a simplified version of part of my prompt:
PS1='$(((SHLVL>1))&&echo $SHLVL)\$ '
If I'm not in a nested shell, it doesn't add anything extra, but it shows the depth if I'm in any level of nesting.
Look at $0: if it starts with a minus -, you're in the login shell.
pstree -s $$ is quite useful to see your depth.
The environment variable $SHLVL contains the shell "depth".
echo $SHLVL
The shell depth can also be determined using pstree (version 23 and above):
pstree -s $$ | grep sh- -o | wc -l
I've found the second way to be more robust than the first whose value was reset when using sudo or became unreliable with env -i.
None of them can correctly deal with su.
The information can be made available in your prompt:
PS1='\u#\h/${SHLVL} \w \$ '
PS1='\u#\h/$(pstree -s $$ | grep sh- -o | tail +2 | wc -l) \w \$ '
The | tail +2 is there to remove one line from the grep output. Since we are using a pipeline inside a "$(...)" command substitution, the shell needs to invoke a sub-shell, so pstree report it and grep detects one more sh- level.
In debian-based distributions, pstree is part of the package psmisc. It might not be installed by default on non-desktop distributions.
As #John Kugelman says, echo $SHLVL will tell you the bash shell depth.
And as #Dennis Williamson shows, you can edit your prompt via the PS1 variable to get it to print this value.
I prefer that it always prints the shell depth value, so here's what I've done: edit your "~/.bashrc" file:
gedit ~/.bashrc
and add the following line to the end:
export PS1='\$SHLVL'":$SHLVL\n$PS1"
Now you will always see a printout of your current bash level just above your prompt. Ex: here you can see I am at a bash level (depth) of 2, as indicated by the $SHLVL:2:
$SHLVL:2
7510-gabriels ~ $
Now, watch the prompt as I go down into some bash levels via the bash command, then come back up via exit. Here you see my commands and prompt (response), starting at level 2 and going down to 5, then coming back up to level 2:
$SHLVL:2
7510-gabriels ~ $ bash
$SHLVL:3
7510-gabriels ~ $ bash
$SHLVL:4
7510-gabriels ~ $ bash
$SHLVL:5
7510-gabriels ~ $ exit
exit
$SHLVL:4
7510-gabriels ~ $ exit
exit
$SHLVL:3
7510-gabriels ~ $ exit
exit
$SHLVL:2
7510-gabriels ~ $
Bonus: always show in your terminal your current git branch you are on too!
Make your prompt also show you your git branch you are working on by using the following in your "~/.bashrc" file instead:
git_show_branch() {
__gsb_BRANCH=$(git symbolic-ref -q --short HEAD 2>/dev/null)
if [ -n "$__gsb_BRANCH" ]; then
echo "$__gsb_BRANCH"
fi
}
export PS1="\e[7m\$(git_show_branch)\e[m\n\h \w $ "
export PS1='\$SHLVL'":$SHLVL $PS1"
Source: I have no idea where git_show_branch() originally comes from, but I got it from Jason McMullan on 5 Apr. 2018. I then added the $SHLVL part shown above just last week.
Sample output:
$SHLVL:2 master
7510-gabriels ~/GS/dev/temp $
And here's a screenshot showing it in all its glory. Notice the git branch name, master, highlighted in white!
Update to the Bonus section
I've improved it again and put my ~/.bashrc file on github here. Here's a sample output of the new terminal prompt. Notice how it shows the shell level as 1, and it shows the branch name of the currently-checked-out branch (master in this case) whenever I'm inside a local git repo!:
Cross-referenced:
Output of git branch in tree like fashion
ptree $$ will also show you how many levels deep you are
If you running inside sub-shell following code will yield 2:
ps | fgrep bash | wc -l
Otherwise, it will yield 1.
EDIT Ok, it's not so robust approach as was pointed out in comments :)
Another thing to try is
ps -ef | awk '{print $2, " ", $8;}' | fgrep $PPID
will yield 'bash' if you in sub-shell.