gsh

Go+ DevOps Tools

This is an alternative to writing shell scripts.

Yes, now you can write shell script in Go+. It supports all shell commands.

Usage

First, let's create a file named example.gsh and write the following code:

mkdir "testgsh"

You don't need a go.mod file, just enter gop run ./example.gsh directly to run.

It's strange to you that the file extension of Go+ source is not .gop but .gsh. It is only because Go+ register .gsh as a builtin classfile.

We can change example.gsh more complicated:

type file struct {
	name  string
	fsize int
}

mkdir! "testgsh"

mkdir "testgsh2"
lastErr!

mkdir "testgsh3"
if lastErr != nil {
	panic lastErr
}

capout => { ls }
echo output.fields

capout => { ls "-l" }
files := [file{flds[8], flds[4].int!} for e <- output.split("\n") if flds := e.fields; flds.len > 2]
echo files

rmdir "testgsh", "testgsh2", "testgsh3"

Execute shell commands

There are many ways to execute shell commands. The simplest way is:

mkdir "testgsh"

It is equivalent to:

exec "mkdir", "testgsh"

or:

exec "mkdir testgsh"

If a shell command is a Go/Go+ language keyword (eg. go), or the command is a relative or absolute path, you can only execute it in the latter two ways:

exec "go", "version"
exec "./test.sh"
exec "/usr/bin/env gop run ."

You can also specify environment variables to run:

exec "GOOS=linux GOARCH=amd64 go install ."

Retrieve environment variables

You can get the value of an environment variable through ${XXX} or $XXX. For example:

echo ${HOME}
ls $HOME

You can also use exec command through $XXX:

exec "ls $HOME"

Check last error

If we want to ensure mkdir successfully, there are three ways:

The simplest way is:

mkdir! "testsh"  # will panic if mkdir failed

The second way is:

mkdir "testsh"
lastErr!

Yes, gsh provides lastErr to check last error.

The third way is:

mkdir "testsh"
if lastErr != nil {
    panic lastErr
}

This is the most familiar way to Go developers.

Capture output of commands

And, gsh provides a way to capture output of commands:

capout => {
    ...
}

Similar to lastErr, the captured output result is saved to output.

For example:

capout => { ls "-l" }
echo output

Here is a possible output:

total 72
-rw-r--r--  1 xushiwei  staff  11357 Jun 19 00:20 LICENSE
-rw-r--r--  1 xushiwei  staff    127 Jun 19 10:00 README.md
-rw-r--r--  1 xushiwei  staff    365 Jun 19 00:25 example.gsh
-rw-r--r--  1 xushiwei  staff    126 Jun 19 09:33 go.mod
-rw-r--r--  1 xushiwei  staff    165 Jun 19 09:33 go.sum
-rw-r--r--  1 xushiwei  staff   1938 Jun 19 10:00 gop_autogen.go

We can use Go+ powerful built-in data processing capabilities to process captured output:

type file struct {
	name  string
	fsize int
}

files := [file{flds[8], flds[4].int!} for e <- output.split("\n") if flds := e.fields; flds.len > 2]

In this example, we split output by "\n", and for each entry e, split it by spaces (e.fields) and save into flds. Condition flds.len > 2 is to remove special line of output:

total 72

At last, pick file name and size of all selected entries and save into files.