I'm trying to write a small script to change the current directory to my project directory:
#!/bin/bash
cd /home/tree/projects/java
I saved this file as proj, added execute permission with chmod, and copied it to /usr/bin. When I call it by:
proj, it does nothing. What am I doing wrong?
Shell scripts are run inside a subshell, and each subshell has its own concept of what the current directory is. The cd succeeds, but as soon as the subshell exits, you're back in the interactive shell and nothing ever changed there.
One way to get around this is to use an alias instead:
alias proj="cd /home/tree/projects/java"
You're doing nothing wrong! You've changed the directory, but only within the subshell that runs the script.
You can run the script in your current process with the "dot" command:
. proj
But I'd prefer Greg's suggestion to use an alias in this simple case.
The cd in your script technically worked as it changed the directory of the shell that ran the script, but that was a separate process forked from your interactive shell.
A Posix-compatible way to solve this problem is to define a shell procedure rather than a shell-invoked command script.
jhome () {
cd /home/tree/projects/java
}
You can just type this in or put it in one of the various shell startup files.
The cd is done within the script's shell. When the script ends, that shell exits, and then you are left in the directory you were. "Source" the script, don't run it. Instead of:
./myscript.sh
do
. ./myscript.sh
(Notice the dot and space before the script name.)
To make a bash script that will cd to a select directory :
Create the script file
#!/bin/sh
# file : /scripts/cdjava
#
cd /home/askgelal/projects/java
Then create an alias in your startup file.
#!/bin/sh
# file /scripts/mastercode.sh
#
alias cdjava='. /scripts/cdjava'
I created a startup file where I dump all my aliases and custom functions.
Then I source this file into my .bashrc to have it set on each boot.
For example, create a master aliases/functions file: /scripts/mastercode.sh
(Put the alias in this file.)
Then at the end of your .bashrc file:
source /scripts/mastercode.sh
Now its easy to cd to your java directory, just type cdjava and you are there.
You can use . to execute a script in the current shell environment:
. script_name
or alternatively, its more readable but shell specific alias source:
source script_name
This avoids the subshell, and allows any variables or builtins (including cd) to affect the current shell instead.
Jeremy Ruten's idea of using a symlink triggered a thought that hasn't crossed any other answer. Use:
CDPATH=:$HOME/projects
The leading colon is important; it means that if there is a directory 'dir' in the current directory, then 'cd dir' will change to that, rather than hopping off somewhere else. With the value set as shown, you can do:
cd java
and, if there is no sub-directory called java in the current directory, then it will take you directly to $HOME/projects/java - no aliases, no scripts, no dubious execs or dot commands.
My $HOME is /Users/jleffler; my $CDPATH is:
:/Users/jleffler:/Users/jleffler/mail:/Users/jleffler/src:/Users/jleffler/src/perl:/Users/jleffler/src/sqltools:/Users/jleffler/lib:/Users/jleffler/doc:/Users/jleffler/work
Use exec bash at the end
A bash script operates on its current environment or on that of its
children, but never on its parent environment.
However, this question often gets asked because one wants to be left at a (new) bash prompt in a certain directory after execution of a bash script from within another directory.
If this is the case, simply execute a child bash instance at the end of the script:
#!/usr/bin/env bash
cd /home/tree/projects/java
echo -e '\nHit [Ctrl]+[D] to exit this child shell.'
exec bash
To return to the previous, parental bash instance, use Ctrl+D.
Update
At least with newer versions of bash, the exec on the last line is no longer required. Furthermore, the script could be made to work with whatever preferred shell by using the $SHELL environment variable. This then gives:
#!/usr/bin/env bash
cd desired/directory
echo -e '\nHit [Ctrl]+[D] to exit this child shell.'
$SHELL
I got my code to work by using. <your file name>
./<your file name> dose not work because it doesn't change your directory in the terminal it just changes the directory specific to that script.
Here is my program
#!/bin/bash
echo "Taking you to eclipse's workspace."
cd /Developer/Java/workspace
Here is my terminal
nova:~ Kael$
nova:~ Kael$ . workspace.sh
Taking you to eclipe's workspace.
nova:workspace Kael$
simply run:
cd /home/xxx/yyy && command_you_want
When you fire a shell script, it runs a new instance of that shell (/bin/bash). Thus, your script just fires up a shell, changes the directory and exits. Put another way, cd (and other such commands) within a shell script do not affect nor have access to the shell from which they were launched.
You can do following:
#!/bin/bash
cd /your/project/directory
# start another shell and replacing the current
exec /bin/bash
EDIT: This could be 'dotted' as well, to prevent creation of subsequent shells.
Example:
. ./previous_script (with or without the first line)
On my particular case i needed too many times to change for the same directory.
So on my .bashrc (I use ubuntu) i've added the
1 -
$ nano ~./bashrc
function switchp
{
cd /home/tree/projects/$1
}
2-
$ source ~/.bashrc
3 -
$ switchp java
Directly it will do: cd /home/tree/projects/java
Hope that helps!
It only changes the directory for the script itself, while your current directory stays the same.
You might want to use a symbolic link instead. It allows you to make a "shortcut" to a file or directory, so you'd only have to type something like cd my-project.
You can combine Adam & Greg's alias and dot approaches to make something that can be more dynamic—
alias project=". project"
Now running the project alias will execute the project script in the current shell as opposed to the subshell.
You can combine an alias and a script,
alias proj="cd \`/usr/bin/proj !*\`"
provided that the script echos the destination path. Note that those are backticks surrounding the script name.
For example, your script could be
#!/bin/bash
echo /home/askgelal/projects/java/$1
The advantage with this technique is that the script could take any number of command line parameters and emit different destinations calculated by possibly complex logic.
to navigate directories quicky, there's $CDPATH, cdargs, and ways to generate aliases automatically
http://jackndempsey.blogspot.com/2008/07/cdargs.html
http://muness.blogspot.com/2008/06/lazy-bash-cd-aliaes.html
https://web.archive.org/web/1/http://articles.techrepublic%2ecom%2ecom/5100-10878_11-5827311.html
In your ~/.bash_profile file. add the next function
move_me() {
cd ~/path/to/dest
}
Restart terminal and you can type
move_me
and you will be moved to the destination folder.
You can use the operator && :
cd myDirectory && ls
While sourcing the script you want to run is one solution, you should be aware that this script then can directly modify the environment of your current shell. Also it is not possible to pass arguments anymore.
Another way to do, is to implement your script as a function in bash.
function cdbm() {
cd whereever_you_want_to_go
echo "Arguments to the functions were $1, $2, ..."
}
This technique is used by autojump: http://github.com/joelthelion/autojump/wiki to provide you with learning shell directory bookmarks.
You can create a function like below in your .bash_profile and it will work smoothly.
The following function takes an optional parameter which is a project.
For example, you can just run
cdproj
or
cdproj project_name
Here is the function definition.
cdproj(){
dir=/Users/yourname/projects
if [ "$1" ]; then
cd "${dir}/${1}"
else
cd "${dir}"
fi
}
Dont forget to source your .bash_profile
This should do what you want. Change to the directory of interest (from within the script), and then spawn a new bash shell.
#!/bin/bash
# saved as mov_dir.sh
cd ~/mt/v3/rt_linux-rt-tools/
bash
If you run this, it will take you to the directory of interest and when you exit it it will bring you back to the original place.
root#intel-corei7-64:~# ./mov_dir.sh
root#intel-corei7-64:~/mt/v3/rt_linux-rt-tools# exit
root#intel-corei7-64:~#
This will even take you to back to your original directory when you exit (CTRL+d)
I did the following:
create a file called case
paste the following in the file:
#!/bin/sh
cd /home/"$1"
save it and then:
chmod +x case
I also created an alias in my .bashrc:
alias disk='cd /home/; . case'
now when I type:
case 12345
essentially I am typing:
cd /home/12345
You can type any folder after 'case':
case 12
case 15
case 17
which is like typing:
cd /home/12
cd /home/15
cd /home/17
respectively
In my case the path is much longer - these guys summed it up with the ~ info earlier.
As explained on the other answers, you have changed the directory, but only within the sub-shell that runs the script. this does not impact the parent shell.
One solution is to use bash functions instead of a bash script (sh); by placing your bash script code into a function. That makes the function available as a command and then, this will be executed without a child process and thus any cd command will impact the caller shell.
Bash functions :
One feature of the bash profile is to store custom functions that can be run in the terminal or in bash scripts the same way you run application/commands this also could be used as a shortcut for long commands.
To make your function efficient system widely you will need to copy your function at the end of several files
/home/user/.bashrc
/home/user/.bash_profile
/root/.bashrc
/root/.bash_profile
You can sudo kwrite /home/user/.bashrc /home/user/.bash_profile /root/.bashrc /root/.bash_profile to edit/create those files quickly
Howto :
Copy your bash script code inside a new function at the end of your bash's profile file and restart your terminal, you can then run cdd or whatever the function you wrote.
Script Example
Making shortcut to cd .. with cdd
cdd() {
cd ..
}
ls shortcut
ll() {
ls -l -h
}
ls shortcut
lll() {
ls -l -h -a
}
If you are using fish as your shell, the best solution is to create a function. As an example, given the original question, you could copy the 4 lines below and paste them into your fish command line:
function proj
cd /home/tree/projects/java
end
funcsave proj
This will create the function and save it for use later. If your project changes, just repeat the process using the new path.
If you prefer, you can manually add the function file by doing the following:
nano ~/.config/fish/functions/proj.fish
and enter the text:
function proj
cd /home/tree/projects/java
end
and finally press ctrl+x to exit and y followed by return to save your changes.
(NOTE: the first method of using funcsave creates the proj.fish file for you).
You need no script, only set the correct option and create an environment variable.
shopt -s cdable_vars
in your ~/.bashrc allows to cd to the content of environment variables.
Create such an environment variable:
export myjava="/home/tree/projects/java"
and you can use:
cd myjava
Other alternatives.
Note the discussion How do I set the working directory of the parent process?
It contains some hackish answers, e.g.
https://stackoverflow.com/a/2375174/755804 (changing the parent process directory via gdb, don't do this) and https://stackoverflow.com/a/51985735/755804 (the command tailcd that injects cd dirname to the input stream of the parent process; well, ideally it should be a part of bash rather than a hack)
It is an old question, but I am really surprised I don't see this trick here
Instead of using cd you can use
export PWD=the/path/you/want
No need to create subshells or use aliases.
Note that it is your responsibility to make sure the/path/you/want exists.
I have to work in tcsh, and I know this is not an elegant solution, but for example, if I had to change folders to a path where one word is different, the whole thing can be done in the alias
a alias_name 'set a = `pwd`; set b = `echo $a | replace "Trees" "Tests"` ; cd $b'
If the path is always fixed, the just
a alias_name2 'cd path/you/always/need'
should work
In the line above, the new folder path is set
This combines the answer by Serge with an unrelated answer by David. It changes the directory, and then instead of forcing a bash shell, it launches the user's default shell. It however requires both getent and /etc/passwd to detect the default shell.
#!/usr/bin/env bash
cd desired/directory
USER_SHELL=$(getent passwd <USER> | cut -d : -f 7)
$USER_SHELL
Of course this still has the same deficiency of creating a nested shell.
There have been a lot of posts about how to overload commands in Bash, either by creating an alias or function, or just changing the script itself or how it is called; these methods make perfect sense to me but don't apply to the problem I'm trying to solve.
It is common in the semiconductor industry to work with EDA tools that provide API commands inside a Tcl interpreter; in my case the EDA tool generates a Bash script, then executes it one API call, so I only have access to the script after the script executed and cannot modify how it is called since that happens under the hood; there is also no blessed method for modifying the commands of interest that are written into the script.
What complicates this further is that this script is generated and called by the EDA tool inside a Singularity container; also, the command that is being called resides in a different EDA tool container, so this command 'vsim' must be transformed into an ssh call to our workload manager (slurm). Example:
vsim <args>
Must be converted to:
ssh <some-host> <ssh-options> "srun <srun-options> vsim <args>"
Again, setting an alias or function called 'vsim' in the parent shell didn't work for me; the alias/function was not inherited by the subprocess (this is difficult for me to accept). I also tried creating a symlink called 'vlog' that pointed at a static dispatcher script; this worked by I'd rather not hard code the path to the dispatcher as a file path; I would rather use a variable, like vlog -> .../<resource>/$VERSION/bin/dispatch_for_flows, but symlinks are not dynamic.
I'm thinking that I should still use the symlink approach but instead of pointing at the dispatcher, I'd point at a wrapper that does a single line exec of an interpolated path to the dispatcher, but I'm still not believing that setting an alias didn't solve the problem. For years I wrote Csh scripts with full paths to commands to get around user aliases; with Bash, it looks like aliases are not inherited ever, even with the shopt 'expanand_alias' on in the parent shell or even in /etc/profile. What am I missing here?
Can someone get the example below to work? I'd like the script to inherit the alias from the parent shell and execute without the "command not found" error, without modification to the script or how it is called. Again, I have no access to the script before it is executed and can't control how it is called; bash is the parent shell, bash is the script, and I do have root access on the OS so I could change the version of bash if neccessary (using 4.4.19(1)-release (x86_64-redhat-linux-gnu))
$ alias hello='echo world'
$ hello
world
$ shopt | grep expand_aliases
expand_aliases on
$ cat test.bash
#!/usr/bin/bash
set -x
alias
shopt | grep expand_aliases
shopt -s expand_aliases
shopt | grep expand_aliases
hello
$ ./test.bash
+ alias
+ shopt
+ grep expand_aliases
expand_aliases off
+ shopt -s expand_aliases
+ shopt
+ grep expand_aliases
expand_aliases on
+ hello
./test.bash: line 7: hello: command not found
Can someone get the example below to work?
No that's not possible with aliases - you can't export an alias. But you can export a function.
$ hello() { echo world; }
$ export -f hello
$ ./test.bash
world
You can create a custom command in PATH:
$ printf "%s\n" "#!/bin/bash" "echo world" > /usr/local/bin/hello
$ chmod +x /usr/local/bin/hello
and similarly add a custom command and add new path with the command to PATH and export.
I've been using letsencrypt to generate SSL certificates for my site, more specifically letsencrypt_webfaction. When I run this command in my project, it works
letsencrypt_webfaction --letsencrypt_account_email <Email I use> --domains <domains I use> --public <public_file> --username <username> --password <password>
However, when I run the same command in a bash script, I get the error
generate_certificate.sh: line 2: letsencrypt_webfaction: command not found
I made sure I had all possible permissions on the bash script using chmod 777 generate_certificate.sh, but still nothing. On top of that I have a bash script that runs right before that, which simply restarts Apache, and that works fine.
I read other S.O articles, such as this one, and tried running dos2unix script.sh, which did run successfully, but when I tried running the bash script again, it didn't work.
Restart Apache Script
#!/bin/bash
../apache2/bin/./restart
#END
Generate SSL Script
#!/bin/bash
letsencrypt_webfaction --letsencrypt_account_email <Email I use> --domains <domains I use> --public <public_file> --username <username> --password <password>
#END
I'm a python developer, and don't have much experience with Ruby, so excuse my ignorance, but the letsencrypt_webfaction command is a function in my bash profile.
~/.bash_profile
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
function letsencrypt_webfaction {
PATH=$PATH:$GEM_HOME/bin GEM_HOME=$HOME/.letsencrypt_webfaction/gems RUBYLIB=$GEM_HOME/lib ruby2.2 $HOME/.letsencrypt_webfaction/gems/bin/letsencrypt_webfaction $*
}
eval "$(rbenv init -)"
PATH=$PATH:$HOME/bin
export PATH
export PATH="$HOME/.rbenv/bin:$PATH"
export TMPDIR="/home/doc4design/src/tmp"
By default, shell functions are only available in the shell they were defined in; they're not inherited by subprocesses. Your .bash_profile is only run by the login shell, not shells that run as subprocesses (e.g. to run scripts).
Option 1: In bash, you can run export -f letsencrypt_webfaction in the defining shell (i.e. in your .bash_profile), and it'll be inherited by subprocesses (provided they're also running bash).
Option 2: You can define the function in your .bashrc instead of .bash_profile, and since you run .bashrc from .bash_profile it'll get defined in all your bash shells.
Option 3: Just use the full command in the script. This would be my preference, since it makes the script more independent. Having a script depend on a shell function that's defined in a completely different place is fragile (as you're experiencing) and just a bit weird.
While I'm at it, here are some general scripting recommendations:
In most contexts, you should put double-quotes around variable references (and strings that contain variable references) to avoid weird effects from word splitting and wildcard expansion. The right side of an assignment is one place it's ok to leave them off (e.g. PATH=$PATH:$HOME/bin and PATH="$PATH:$HOME/bin" are both ok), but I tend to recommend using quotes everywhere as it's hard to keep track of where it's safe to leave them off and where it's dangerous. For the same reason, you should almost always use "$#" instead of $* (as in the letsencrypt_webfaction function).
shellcheck.net is really good at spotting errors like this, so I recommend running your shell scripts through it and acting on its suggestions.
Using the function keyword to define a function is nonstandard; the standard syntax is to use () after the function name, like this:
letsencrypt_webfaction() {
PATH="$PATH:$GEM_HOME/bin" GEM_HOME="$HOME/.letsencrypt_webfaction/gems" RUBYLIB="$GEM_HOME/lib" ruby2.2 "$HOME/.letsencrypt_webfaction/gems/bin/letsencrypt_webfaction" "$#"
}
The function I just gave still may not work right, since it (re)defines GEM_HOME after using it. The entire line gets parsed (and pre-existing variable definitions expanded), then the variables defined as prefixes to the command get included in the environment of the command. This means that the ruby script gets the updated value of GEM_HOME, but the updated values of PATH and RUBYLIB are based on whatever value GEM_HOME had when the function was run. I'm pretty sure this is not what you intended.
In the restart apache script, you use a relative path to the restart command. This will be evaluated relative to the working directory of the process that runs the script, not relative to the script's location. This could be anywhere.
I am attempting to write a bash command line tool that is usable immediately after installation, i.e. in the same shell as its installation script was called. Lets say install-script.sh (designed for Ubuntu) looks like:
# Get the script's absolute path:
pushd `dirname $0` > /dev/null
SCRIPTPATH=`pwd`
popd > /dev/null
# Add lines to bash.bashrc to export the environment variable:
echo "SCRIPT_HOME=${SCRIPTPATH}" >> /etc/bash.bashrc
echo "export SCRIPT_HOME" >> /etc/bash.bashrc
# Create a new command:
cp ${SCRIPTPATH}/newcomm /usr/bin
chmod a+x /usr/bin/newcomm
The idea is that the new command newcomm uses the SCRIPT_HOME environment variable to reference the main script - which is also in SCRIPTPATH:
exec "${SCRIPT_HOME}/main-script.sh"
Now, the updated bash.bashrc hasn't been loaded into the parent shell yet. Worse, I cannot source it from within the script - which is running in a child shell. Using export to change SCRIPT_HOME in the parent shell would at best be duct-taping the issue, but even this is impossible. Also note that the installation script needs to be run using sudo so it cannot be called from the parent shell using source.
It should be possible since package managers like apt do it. Is there a robust way to patch up my approach? How is this usually done, and is there a good guide to writing bash installers?
You can't. Neither can apt.
A package manager will instead just write required data/variables to a file, which are read either by the program itself, by a patch to the program, or by a wrapper.
Good examples can be found in /etc/default/*. These are files with variable definitions, and some even helpfully describe where they're sourced from:
$ cat /etc/default/ssh
# Default settings for openssh-server. This file is sourced by /bin/sh from
# /etc/init.d/ssh.
# Options to pass to sshd
SSHD_OPTS=
You'll notice that none of the options are set in your current shell after installing a package, since programs get them straight from the files in one way or another.
The only way to modify the current shell is to source a script. That's unavoidable, so start there. Write a script that is sourced. That script will in turn call your current script.
Your current script will need to communicate with the sourced one to tell it what to change. A common way is to echo variable assignments that can be directly executed by the caller. For instance:
printf 'export SCRIPT_HOME=%q\n' "$SCRIPTPATH"
Using printf with %q ensures any special characters will be escaped properly.
Then have the sourced script eval the inner script.
eval "$(sudo install-script.sh)"
If you want to hide the sourceing of the top script you could hide it behind an alias or shell function.
This question already has answers here:
Multiple commands in an alias for bash
(10 answers)
Closed 4 years ago.
I know how to configure aliases in bash, but is there a way to configure an alias for a sequence of commands?
I.e say I want one command to change to a particular directory, then run another command.
In addition, is there a way to setup a command that runs "sudo mycommand", then enters the password? In the MS-DOS days I'd be looking for a .bat file but I'm unsure of the linux (or in this case Mac OSX) equivalent.
For chaining a sequence of commands, try this:
alias x='command1;command2;command3;'
Or you can do this:
alias x='command1 && command2 && command3'
The && makes it only execute subsequent commands if the previous returns successful.
Also for entering passwords interactively, or interfacing with other programs like that, check out expect. (http://expect.nist.gov/)
You mention BAT files so perhaps what you want is to write a shell script. If so then just enter the commands you want line-by-line into a file like so:
command1
command2
and ask bash to execute the file:
bash myscript.sh
If you want to be able to invoke the script directly without typing "bash" then add the following line as the first line of the file:
#! /bin/bash
command1
command2
Then mark the file as executable:
chmod 755 myscript.sh
Now you can run it just like any other executable:
./myscript.sh
Note that unix doesn't really care about file extensions. You can simply name the file "myscript" without the ".sh" extension if you like. It's that special first line that is important. For example, if you want to write your script in the Perl programming language instead of bash the first line would be:
#! /usr/bin/perl
That first line tells your shell what interpreter to invoke to execute your script.
Also, if you now copy your script into one of the directories listed in the $PATH environment variable then you can call it from anywhere by simply typing its file name:
myscript.sh
Even tab-completion works. Which is why I usually include a ~/bin directory in my $PATH so that I can easily install personal scripts. And best of all, once you have a bunch of personal scripts that you are used to having you can easily port them to any new unix machine by copying your personal ~/bin directory.
it's probably easier to define functions for these types of things than aliases, keeps things more readable if you want to do more than a command or two:
In your .bashrc
perform_my_command() {
pushd /some_dir
my_command "$#"
popd
}
Then on the command line you can simply do:
perform_my_command my_parameter my_other_parameter "my quoted parameter"
You could do anything you like in a function, call other functions, etc.
You may want to have a look at the Advanced Bash Scripting Guide for in depth knowledge.
For the alias you can use this:
alias sequence='command1 -args; command2 -args;'
or if the second command must be executed only if the first one succeeds use:
alias sequence='command1 -args && command2 -args'
Your best bet is probably a shell function instead of an alias if the logic becomes more complex or if you need to add parameters (though bash supports aliases parameters).
This function can be defined in your .profile or .bashrc. The subshell is to avoid changing your working directory.
function myfunc {
( cd /tmp; command )
}
then from your command prompt
$ myfunc
For your second question you can just add your command to /etc/sudoers (if you are completely sure of what you are doing)
myuser ALL = NOPASSWD: \
/bin/mycommand
Apropos multiple commands in a single alias, you can use one of the logical operators to combine them. Here's one to switch to a directory and do an ls on it
alias x="cd /tmp && ls -al"
Another option is to use a shell function. These are sh/zsh/bash commands. I don't know enough of other shells to be sure if they work.
As for the sudo thing, if you want that (although I don't think it's a good idea), the right way to go is to alter the /etc/sudoers file to get what you want.
You can embed the function declaration followed by the function in the alias itself, like so:
alias my_alias='f() { do_stuff_with "$#" (arguments)" ...; }; f'
The benefit of this approach over just declaring the function by itself is that you can have a peace of mind that your function is not going to be overriden by some other script you're sourcing (or using .), which might use its own helper under the same name.
E.g., Suppose you have a script init-my-workspace.sh that you're calling like . init-my-workspace.sh or source init-my-workspace.sh whose purpose is to set or export a bunch of environment variables (e.g., JAVA_HOME, PYTHON_PATH etc.). If you happen to have a function my_alias inside there, as well, then you're out of luck as the latest function declaration withing the same shell instance wins.
Conversely, aliases have separate namespace and even in case of name clash, they are looked up first. Therefore, for customization relevant to interactive usage, you should only ever use aliases.
Finally, note that the practice of putting all the aliases in the same place (e.g., ~/.bash_aliases) enables you to easily spot any name clashes.
you can also write a shell function; example for " cd " and "ls " combo here