go - How to use a file as stdin when exec a command -

i have simple code:

cmd := exec.command("cat") cmd.stdout = os.stdout stdin, _ := cmd.stdinpipe() file, _ := os.open("file") io.copy(stdin, file) _ = cmd.run() 

it works. problem cmd.run() never returns. seems after writing file stdin, cat still waits more content.

i'm trying cat <file does, in case cat exit after reading file.

i wonder how achieve in go?

it's because you don't close stdin. add stdin.close() after io.copy. cat terminate.

also, know it's example there absolutely no error checking. assume that's illustration purposes. :-)