Access command line arguments in Julia

Question

When I type in

$ julia myprog.jl foo bar baz

Where in my code can I go to access the strings \"foo\", \"bar\", \"baz\" ?

Answer 1

Ah, more web-searching led to the right answer. The keyword ARGS::Array{ASCIIString} holds command line arguments

Here is a simple example

# cli.jl

print(map(x->string(x, x), ARGS))  # Concatenate each arg onto itself and print

Lets test it at the command line:

$ julia cli.jl a b c
aa
bb
cc

Answer 2

A simpler example:

#printargs.jl

println(ARGS[2]);

Run it as

julia printargs.jl a b c d

b

Note that the array index starts from 1 and NOT 0. Thus ARGS[2] prints b and not c as in case of many other programming languages.

Answer 3

https://docs.microsoft.com/en-us/windows/win32/api/processenv/nf-processenv-getcommandlinea

In the case that you really need the exact args that came to julia including the -e, there is a workaround for Windows. Looking at /proc/PID/cmdline you can extract it linux. Mac doesn't have the same /proc option, so asking ps works nicely.

if Sys.iswindows()
    mycmd = unsafe_string(ccall(:GetCommandLineA, Cstring, ()))
elseif Sys.isapple()
    mycmd = strip(read(`/bin/ps -p $(getpid()) -o command=`, String))
elseif Sys.isunix()
    mycmd = replace(read(joinpath("/", "proc", string(getpid()), "cmdline"), String), "\x00"=>" ")
else
    mycmd = string(Base.julia_cmd()) * join(map(x->" " * x, ARGS))
end

But typical use cases you only need to look at ARGS.

Answer 4

julia> Pkg.add("ArgParse") Docs at https://argparsejl.readthedocs.io/en/latest/argparse.html