This question already has an answer here:
Blank first line of shell script: explain behavior of UID variable
(1 answer)
Closed 6 years ago.
Hi I have a question about bash.
and I'm new to it.
I made a file named "test.sh" and its contents is
#!/bin/bash
set -x
echo $UID
echo "$UID"
echo "$(id -u)"
and the result is blank!!
nothing shows up
However, when i just type "echo $UID" on terminal
it shows "1011"
is there anything i missed for bash?
Please help
UPDATED
bash version is 4.3.11 and I typed "sh test.sh" to execute.
and the result is
+ echo
+ echo
+ id -u
+ echo 1011
1011
thanks!
$UID is a Bash variable that is not set under sh, that may be why it outputs blank lines.
Try bash test.sh or make your script executable with chmod u+x test.sh, the program defined in shebang will then be used (/bin/bash)
Related
This question already has answers here:
Difference between sh and Bash
(11 answers)
Pattern matching in UNIX Case statement
(1 answer)
Closed 1 year ago.
I am using this image which has bash v4.3.48 and curl v7.56.1:
https://hub.docker.com/r/bizongroup/alpine-curl-bash/tags?page=1&ordering=last_updated
Inside the docker I write the following script:
email_dest="iz#gmail.com}}"
suffix="#gmail.com"
dm_to=${email_dest%"$suffix"}
if [[ $email_dest == *"#users.noreply.github.com"* ]]
then
echo "Email address is no reply. Please fix your email preferences in Github"
elif [[ $email_dest == *$suffix* ]]
then
curl -X POST -H 'Content-type: application/json' --data '{"text":"Hello <#'"$dm_to"'>. '{{inputs.parameters.workflow_name}}' "}' https://hooks.slack.com/services/T01JNE5DXA7/B0246T84N75/hHDk7RUg2BWl2bYbPoN9r
else
echo "Email address is not of digibank domain!"
fi
If I run this script with bash command <script_name> it will work as expected (Run the curl command). But if I run it with sh command <script_name> it will not run the curl command:
/ # bash send-message.sh
ok/ #
/ # sh send-message.sh
Email address is not of digibank domain!
Any suggestion of what it could be? and what should be changed so it will work with sh?
That lies within the differences between bash and sh:
sh is POSIX compliant, whereas bash isn't (fully).
As a best practice you should always include a shebang:
#!/usr/bin/env bash
echo "this is going to run within bash"
With this you can now omit calling the script via bash myscript and just call it with ./myscript and it is always going to use bash (even if you are in a zsh, sh or whatever else).
However, if you truly want to have a script that runs with both sh and bash then you should rewrite your script to be plain sh compliant (i.e. POSIX).
TL;DR
Any suggestion of what it could be? and what should be changed so it will work with sh?
In your script you are using bash extensions such as [[ which is why it does not work with sh.
Checkout the links I posted above for more differences and how you can "convert" your bash script into a sh script.
The following site has a great summary on what to change in order to get your bash script working for dash which is an implementation of sh: http://mywiki.wooledge.org/Bashism
Furthermore, you can also check if any issues exist by using the following site: https://www.shellcheck.net/
This question already has answers here:
read: Illegal option -d
(2 answers)
Closed 5 years ago.
The following is my code
Read file
Count=0
While read -n1 c
Do
Case $c in
.
.
.
.
Esac
Done < $file
Echo"$count"
When I run this code, it shows the error as
read: Illegal option -n
I'm just started learning shell programming.So please help me fix this code
-n is not an option for read in standard Unix sh and (some of) its variants.
read -n runs well on bash, zsh and ksh93, so you may want to select one of them instead of sh or dash (Debian sh), probably by adding a shebang line:
#! /bin/bash
Or run explicitly with bash:
bash foo.sh
This question already has answers here:
Why should there be spaces around '[' and ']' in Bash?
(5 answers)
Closed 5 years ago.
This is the code of the my shell script:
#! /bin/bash
if ["$SHELL" = "/bin/bash"];then
echo "this is bash"
elif ["$SHELL" = "aa"];then
echo "this is aa"
else
echo "this is not /bin/bash, but $SHELL"
fi
why I execute the test_bash_03 script file gets the else result? shouldn't it be:this is bash ？
aircraftdeMacBook-Pro:bash_demo ldl$ ./test_bash_03
./test_bash_03: line 3: [/bin/bash: No such file or directory
./test_bash_03: line 5: [/bin/bash: No such file or directory
this is not /bin/bash, but /bin/bash
And I echo the $SHELL I also get the /bin/bash
aircraftdeMacBook-Pro:bash_demo ldl$ echo $SHELL
/bin/bash
You are missing a space after [ and before ].
The bash tries to execute a command named [/bin/bash instead of [ (which is test), then doesn't find that and has an exit code of 1 (false). So you end up in the else case.
This question already has answers here:
Difference between single and double quotes in Bash
(7 answers)
Closed 6 years ago.
I try to have a script to add ips to /etc/hosts, but if it does add a line to /etc/hosts, the line is empty.
I guess there is an issue with the variable name exchanged by value into the ["] :
machines=("dell" "pb")
ips=( "192.168.0.70" "192.168.0.60")
n=-1
for nom_machine in "${machines[#]}"
do
n=$(( $n + 1 ))
ip_machine=${ips[$n]}
link=" $ip_machine $nom_machine"
$(sudo /bin/bash -c 'echo -e $link >> /etc/hosts')
done
Any idea why this add empty lines to /etc/hosts ?
Variables aren't expanded in single quotes, only double quotes. You also don't need the $(...) around sudo.
sudo bash -c "echo -e $link >> /etc/hosts"
As a script style issue, I would suggest removing the sudo call altogether. Instead, expect the person running the script run it with sudo if they don't have sufficient permissions. Your script would just have:
echo -e "$link" >> /etc/hosts
#!/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