how to make golang execute a string

Question

I am not asking to make golang do some sort of "eval" in the current context, just need it to take a input string (say, received from network) and execute it as a separate golang program.

In theory, when you run go run testme.go, it will read the content of testme.go into a string and parse, compile and execute it. Wonder if it is possible to call a go function to execute a string directly. Note that I have a requirement not to write the string into a file.

UPDATE1

I really want to find out if there is a function (in some go package) that serves as an entry point of go, in another word, I can call this function with a string as parameter, it will behave like go run testme.go, where testme.go has the content of that string.

Where does the requirement to not write intermediate files comes from? — fuz
– fuz, Commented Feb 28, 2015 at 19:47

Not_a_Golfer · Accepted Answer · 2015-02-28 16:28:38Z

4

AFAIK it cannot be done, and the go compiler has to write intermediate files, so even if you use go run and not go build, files are created for the sake of running the code, they are just cleaned up if necessary. So you can't run a go program without touching the disk, even if you manage to somehow make the compiler take the source not from a file.

For example, running strace on calling go run on a simple hello world program, shows among other things, the following lines:

mkdir("/tmp/go-build167589894", 0700) 
// ....
mkdir("/tmp/go-build167589894/command-line-arguments/_obj/exe/", 0777) 
// ... and at the end of things
unlink("/tmp/go-build167589894/command-line-arguments/_obj/exe/foo") 
// ^^^ my program was called foo.go
// ....
// and eventually:
rmdir("/tmp/go-build167589894")

So you can see that go run does a lot of disk writing behind the scenes, just cleans up afterwards.

I suppose you can mount some tmpfs and build in it if you wish, but otherwise I don't believe it's possible.

answered Feb 28, 2015 at 16:28

Not_a_Golfer

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6 Comments

packetie Over a year ago

Thanks @Not_a_Golfer for the idea of using strace. Sounds like the only possibility is to create ramdisk so go will write the intermediate files in thse ramdisk. Wonder if there is a package for it.

OneOfOne Over a year ago

@codingFun on most recent linux distros, /tmp is a ramdisk (tmpfs).

Mr_Pink Over a year ago

@OneOfOne: that's far from universally true. Most do have a block of shared memory mapped to /run/shm, or /dev/shm though.

OneOfOne Over a year ago

@JimB good to know, I'm personally using arch and tried 1 or 2 other that had it that way too.

packetie Over a year ago

Thanks guys for the points. I have clarified the question with update1.

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user9123 · Accepted Answer · 2020-05-04 11:20:49Z

3

I know that this question is (5 years) old but I wanted to say that actually, it is possible now, for anyone looking for an up-to-date answer.

The Golang compiler is itself written in Go so can theoretically be embedded in a Go program. This would be quite complicated though.

As a better alternative, there are projects like yaegi which are effectively a Go interpreter which can be embedded into Go programs.

answered May 4, 2020 at 11:20

user9123

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