I am attempting to store the result of an echo command as a variable to be used in a shell script. Debian 4.19.0-6-amd64
The command works in terminal: echo $HOSTNAME returns debian-base, the correct hostname.
I attempt to run it in a shell script, such as:
#!/usr/bin/bash
CURRENT_HOSTNAME=`echo $HOSTNAME`
echo $CURRENT_HOSTNAME
I have tried expansion:
CURRENT_HOSTNAME=$(echo $HOSTNAME)
And just to cover some more bases, I tried things like:
CURRENT_HOSTNAME=$HOSTNAME
# or
CURRENT_HOSTNAME="$HOSTNAME"
# also, in case a problem with reserved names:
test=$HOSTNAME
test="$HOSTNAME"
Works great in the terminal! Output is as follows:
root#debian-base:/scripts# echo $HOSTNAME
debian-base
root#debian-base:/scripts# TEST_HOSTNAME=$HOSTNAME
root#debian-base:/scripts# echo $TEST_HOSTNAME
debian-base
root#debian-base:/scripts# TEST_TWO_HOSTNAME=$(echo $HOSTNAME)
root#debian-base:/scripts# echo $TEST_TWO_HOSTNAME
debian-base
As soon as I run the script (as above):
root#debian-base:/scripts# sh test.sh
root#debian-base:/scripts#
What am I doing wrong?
You are using bash as your terminal. Bash has the variable $HOSTNAME set. You run your script with sh. sh does not have a $HOSTNAME.
Options:
bash test.sh
Or run it as a program:
chmod +x test.sh
./test.sh
But I think you need to change your first line to:
#!/bin/bash
As I don't think bash is installed in /usr/bin in most cases. But you need to try. To figure out where bash is installed use which bash
Another option is to use the hostname binary:
CURRENT_HOSTNAME=$(hostname)
echo $CURRENT_HOSTNAME
Which works in both bash and sh.
You can start sh by just running sh. You will see it has a bash-like terminal. You can try to do echo $HOSTNAME. It will not show, because it's not there. You can use set to see all the variables that are there (as sh does not have tab completion it's harder to figure out).
I want to execute Zsh function command in Bash script. Here is an example:
~/.zshrc
hello () {
echo "Hello!"
}
hello.sh
#!/bin/bash
hello
executing above bash script in zsh
(zsh) $ ./hello.sh
hello command not found
I also tried with heredocs:
#!/bin/bash
/bin/zsh - <<'EOF'
hello
EOF
executing above script with heredocs also says command not found error.
Any suggestions?
Thanks!
You can use it like that :
#!/bin/bash
/bin/zsh -i -c hello
-i : Force shell to be interactive
Then, if the shell is interactive, commands are read from /etc/zshrc and then $ZDOTDIR/.zshrc (this is usually your $HOME/.zshrc)
-c : Run a command in this shell
I am trying to do the following:
if ps aux | grep "[t]ransporter_pulldown.py" > /dev/null
then
echo "Script is already running. Skipping"
else
exec "sudo STAGE=production $DIR/transporter_pulldown.py" # this line errors
fi
$ sudo STAGE=production $DIR/transporter_pulldown.py works on the command line, but in a bash script it gives me:
./transporter_pulldown.sh: line 9:
exec: /Users/david/Desktop/Avails/scripts/STAGE=production
/Users/david/Desktop/Avails/scripts/transporter_pulldown.py:
cannot execute: No such file or directory
What would be the correct syntax here?
sudo isn't a command interpreter thus its trying to execute the first argument as a command.
Instead try this:
exec sudo bash -c "STAGE=production $DIR/transporter_pulldown.py"
This creates uses a new bash processes to interpret the variables and execute your python script. Also note that $DIR will be interpreted by the shell you're typing in rather than the shell that is being executed. To force it to be interpreted in the new bash process use single quotes.
This question already has answers here:
How to use aliases defined in .bashrc in other scripts?
(6 answers)
Closed 2 years ago.
My alias defined in a sample shell script is not working. And I am new to Linux Shell Scripting.
Below is the sample shell file
#!/bin/sh
echo "Setting Sample aliases ..."
alias xyz="cd /home/usr/src/xyz"
echo "Setting done ..."
On executing this script, I can see the echo messages. But if I execute the alias command, I see the below error
xyz: command not found
am I missing something ?
source your script, don't execute it like ./foo.sh or sh foo.sh
If you execute your script like that, it is running in sub-shell, not your current.
source foo.sh
would work for you.
You need to set a specific option to do so, expand_aliases:
shopt -s expand_aliases
Example:
# With option
$ cat a
#!/bin/bash
shopt -s expand_aliases
alias a="echo b"
type a
a
$ ./a
# a is aliased to 'echo b'
b
# Without option
$ cat a
#!/bin/bash
alias a="echo b"
type a
a
$ ./a
./a: line 3: type: a: not found
./a: line 4: a: command not found
reference: https://unix.stackexchange.com/a/1498/27031 and https://askubuntu.com/a/98786/127746
sourcing the script source script.sh
./script.sh will be executed in a sub-shell and the changes made apply only the to sub-shell. Once the command terminates, the sub-shell goes and so do the changes.
OR
HACK: Simply run following command on shell and then execute the script.
alias xyz="cd /home/usr/src/xyz"
./script.sh
To unalias use following on shell prompt
unalias xyz
If you execute it in a script, the alias will be over by the time the script finishes executing.
In case you want it to be permanent:
Your alias is well defined, but you have to store it in ~/.bashrc, not in a shell script.
Add it to that file and then source it with . .bashrc - it will load the file so that alias will be possible to use.
In case you want it to be used just in current session:
Just write it in your console prompt.
$ aa
The program 'aa' is currently not installed. ...
$
$ alias aa="echo hello"
$
$ aa
hello
$
Also: From Kent answer we can see that you can also source it by source your_file. In that case you do not need to use a shell script, just a normal file will make it.
You may use the below command.
shopt -s expand_aliases
source ~/.bashrc
eval $command
Your alias has to be in your .profile file not in your script if you are calling it on the prompt.
If you put an alias in your script then you have to call it within your script.
Source the file is the correct answer when trying to run a script that inside has an alias.
source yourscript.sh
Put your alias in a file call ~/.bash_aliases and then, on many distributions, it will get loaded automatically, no need to manually run the source command to load it.
#!/bin/bash
ARRAYNAME=( 'time1' 'life' 'time2' )
echo ${ARRAYNAME[1]}
In the above code when i run my script as
$ sh ex1.sh
it gives an error message:
ex1.sh: 2: Syntax error: "(" unexpected
Why is this?
sh on your system is not bash.
Your "shebang" lines uses bash shell ("/bin/bash") but you're probably invoking another shell ("sh") invoking another shell to execute your script. Try this :
$ chmod 700 ex1.sh
This will make your script executable. Then run it :
$ ./ex1.sh