Run a bash file with parameters with Go

Question

I am trying to run a bash script that has parameters like so:

./test.sh param1 param2

bash file

param1=$1
param2=$2

echo $param1
echo $param2

However it does not work but it will work if the params are not there.

cmd, _ := exec.Command("/bin/sh", fmt.Sprintf("./test.sh %s %s","test1","test2")).Output()

But if I change the bash script to do something else without passing anything into it, then it works.

cmd, _ := exec.Command("/bin/sh", "./test.sh").Output()

How can I pass parameters into a bash file with Go?

sh should never be used to run a bash file. sh and bash are two different shells -- even on operating systems where they're symlinked, starting bash under the name sh disables some of its features. — Charles Duffy
– Charles Duffy, Commented Jul 29, 2021 at 17:16
The quotes are not quite right, as can be seen from the syntax highlighting here in the post. — mkrieger1
– mkrieger1, Commented Jul 29, 2021 at 17:16
Anyhow -- if you were Doing It Right, you'd have a shebang in your script and wouldn't specify an explicit interpreter at all in the caller. — Charles Duffy
– Charles Duffy, Commented Jul 29, 2021 at 17:17
That is to say, make the script start with #!/bin/sh (if it's really a sh script instead of a bash script), give it executable permissions, and then start exec.Command('./test.sh', "test1", "test2"). (Ideally, you shouldn't have a .sh extension on the filename either -- see commandname extensions considered harmful for an extensive essay on the topic; using extensions means you can't change your script's interpreter without making the extension misleading or also changing every caller). — Charles Duffy
– Charles Duffy, Commented Jul 29, 2021 at 17:18

Charles Duffy · Accepted Answer · 2021-07-29 17:25:06Z

5

sh expects the name of a script to run as its argument. You don't run sh './test.sh test1 test2' at a shell, you run sh ./test.sh test1 test2. The equivalent to that in Go is:

// KINDA BAD: Doesn't let the script choose its own interpreter
cmd, err := exec.Command("/bin/sh", "./test.sh", "test1", "test2")

If you were passing a shell script as an argument, that would be akin to the shell command sh -c './test.sh test1 test2' -- notice the -c argument. It's very bad practice (introduces serious security bugs), and you shouldn't ever do this, but if you were going to, it would look like:

// VERY BAD: Introduces serious security bugs if arguments are parameterized
cmd, err := exec.Command("/bin/sh", "-c", "./test.sh test1 test2")

But you shouldn't do any of that. Change your script to have a shebang:

#!/bin/sh
param1=$1
param2=$2

echo "$param1"
echo "$param2"

...save it as yourscript (no .sh!), set it to have executable permissions (chmod +x yourscript), and then run:

// GOOD: Lets your script choose its own interpreter
cmd, err := exec.Command("./yourscript", "test1", "test2")

edited Jul 29, 2021 at 17:25

answered Jul 29, 2021 at 17:20

Charles Duffy

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1 Comment

Mike3355 Over a year ago

awesome thanks. I knew it would be simple

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