I have a simple bash script test.sh
#!/bin/sh
# This is a comment
echo "Hi"
It does not execute anything when I try to run ./test.sh
$ ./test.sh
$
It comes with empty output. The mac terminal is executing echo commands but not shell script. I am not sure what I am missing. Please suggest.
to execute command file , type sh test.sh
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).
In a bash script I start a new terminal with a command that gives an error. However I don't seem to be able to grab that error code:
#! /bin/bash
gnome-terminal -x bash -c "cat dksdamfasdlm"
echo $?
Output:
0
So I get the error code of the gnome-terminal command instead of the cat one. One suggestion I got, was to make a file with the code and read that from the parent bash. The problem is that I still seem to not be able and read the error code even that way:
#! /bin/bash
gnome-terminal -x bash -c "cat dksdamfasdlm; echo $?; sleep 2"
Output (on new terminal):
cat: dksdamfasdlm: No such file or directory
0
Why is that? Some suggestion on how to solve this? I just want to somehow grab the error in the new terminal from the parent bash.
It seems GNOME Terminal exits immediately after starting, which is obvious if you run for example gnome-terminal -x sleep 10. Since it doesn't wait for the command to finish, there's no way the return code will be that of the command. I could find no option in gnome-terminal --help-all to keep the process in the foreground.
Regarding your second question, you've double-quoted the command, so $? is expanded before running it. This should work:
gnome-terminal -x bash -c 'cat dksdamfasdlm; echo $?; sleep 2'
PS: The -x option is not documented in GNOME Terminal 3.8.4's gnome-terminal --help-all, various references don't help much, and there's no good explanation for why there's a -e option with identical semantics and different syntax.
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
fi
The above is part of my script. When the current shell is /bin/csh my script fails with the following error:
If: Expression Syntax
Then: Command not found
If I run bash and then run my script, it runs fine(as expected).
So the question is: If there is any way that myscript can change the current shell and then interpretate rest of the code.
PS: If i keep bash in my script, it changes the current shell and rest of the code in script doesn't get executed.
The other replies are correct, however, to answer your question, this should do the trick:
[[ $(basename $SHELL) = 'bash' ]] || exec /bin/bash
The exec builtin replaces the current shell with the given command (in this case, /bin/bash).
You can use SHEBANG(#!) to overcome your issue.
In your code you are already using she-bang but make sure it is first and foremost line.
$ cat test.sh
#!/bin/bash
if [ ! -f readexportfile ]; then
echo "readexportfile does not exist"
exit 0
else
echo "No File"
fi
$ ./test.sh
readexportfile does not exist
$ echo $SHELL
/bin/tcsh
In the above code even though I am using CSH that code executed as we mentioned shebang in the code. In case if there is no shebang then it will take the help of shell in which you are already logged in.
In you case you also check the location of bash interpreter using
$ which bash
or
$ cat /etc/shells |grep bash
I do this in a script:
read direc <<< $(basename `pwd`)
and I get:
Syntax error: redirection unexpected
in an ubuntu machine
/bin/bash --version
GNU bash, version 4.0.33(1)-release (x86_64-pc-linux-gnu)
while I do not get this error in another suse machine:
/bin/bash --version
GNU bash, version 3.2.39(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.
Why the error?
Does your script reference /bin/bash or /bin/sh in its hash bang line? The default system shell in Ubuntu is dash, not bash, so if you have #!/bin/sh then your script will be using a different shell than you expect. Dash does not have the <<< redirection operator.
Make sure the shebang line is:
#!/bin/bash
or
#!/usr/bin/env bash
And run the script with:
$ ./script.sh
Do not run it with an explicit sh as that will ignore the shebang:
$ sh ./script.sh # Don't do this!
If you're using the following to run your script:
sudo sh ./script.sh
Then you'll want to use the following instead:
sudo bash ./script.sh
The reason for this is that Bash is not the default shell for Ubuntu. So, if you use "sh" then it will just use the default shell; which is actually Dash. This will happen regardless if you have #!/bin/bash at the top of your script. As a result, you will need to explicitly specify to use bash as shown above, and your script should run at expected.
Dash doesn't support redirects the same as Bash.
Docker:
I was getting this problem from my Dockerfile as I had:
RUN bash < <(curl -s -S -L https://raw.githubusercontent.com/moovweb/gvm/master/binscripts/gvm-installer)
However, according to this issue, it was solved:
The exec form makes it possible to avoid shell string munging, and
to RUN commands using a base image that does not contain /bin/sh.
Note
To use a different shell, other than /bin/sh, use the exec form
passing in the desired shell. For example,
RUN ["/bin/bash", "-c", "echo hello"]
Solution:
RUN ["/bin/bash", "-c", "bash < <(curl -s -S -L https://raw.githubusercontent.com/moovweb/gvm/master/binscripts/gvm-installer)"]
Notice the quotes around each parameter.
You can get the output of that command and put it in a variable. then use heredoc. for example:
nc -l -p 80 <<< "tested like a charm";
can be written like:
nc -l -p 80 <<EOF
tested like a charm
EOF
and like this (this is what you want):
text="tested like a charm"
nc -l -p 80 <<EOF
$text
EOF
Practical example in busybox under docker container:
kasra#ubuntu:~$ docker run --rm -it busybox
/ # nc -l -p 80 <<< "tested like a charm";
sh: syntax error: unexpected redirection
/ # nc -l -p 80 <<EOL
> tested like a charm
> EOL
^Cpunt! => socket listening, no errors. ^Cpunt! is result of CTRL+C signal.
/ # text="tested like a charm"
/ # nc -l -p 80 <<EOF
> $text
> EOF
^Cpunt!
do it the simpler way,
direc=$(basename `pwd`)
Or use the shell
$ direc=${PWD##*/}
Another reason to the error may be if you are running a cron job that updates a subversion working copy and then has attempted to run a versioned script that was in a conflicted state after the update...
On my machine, if I run a script directly, the default is bash.
If I run it with sudo, the default is sh.
That’s why I was hitting this problem when I used sudo.
In my case error is because i have put ">>" twice
mongodump --db=$DB_NAME --collection=$col --out=$BACKUP_LOCATION/$DB_NAME-$BACKUP_DATE >> >> $LOG_PATH
i just correct it as
mongodump --db=$DB_NAME --collection=$col --out=$BACKUP_LOCATION/$DB_NAME-$BACKUP_DATE >> $LOG_PATH
Before running the script, you should check first line of the shell script for the interpreter.
Eg:
if scripts starts with /bin/bash , run the script using the below command
"bash script_name.sh"
if script starts with /bin/sh, run the script using the below command
"sh script_name.sh"
./sample.sh - This will detect the interpreter from the first line of the script and run.
Different Linux distributions having different shells as default.