more process features

[StefanKarpinski]

Things that are needed:

• writing to file handles: run(echo Hello | fh)
• reading from file handles: run(fh | sort -nr)
• writing to files by name: run(echo Hello > "hello.txt")
• append to files by name: run(echo world >> "hello.txt")
• reading from files by name: run("/usr/share/dict/words" > tr A-Z a-z)
• programmatically writing to a pipeline
• better name than spawn for starting a process without blocking
• make run(cmd) throw an error on failure
• use success(cmd) to just test for success or failure

[JeffBezanson]

I think I'd rather have run return the exit code than have to put a try-catch block around it almost every time.

[StefanKarpinski]

See a9fd119: if you want the success status, use the success function instead. I really think this is the right way to go. I've been bitten by sloppy perl/ruby scripts that swallow failing commands silently far too often. We do not want to repeat that design mistake.

[StefanKarpinski]

Silently swallowing command failure, brittle string interpolation into command strings, and unnecessarily using the shell to spawn external pipelines are my three bugaboos with doing shell-like scripting from ruby and perl. With this, we've eliminated all three.

[JeffBezanson]

Also noting that we need a more abstract interface for fdio(read_from(cmd).fd, true).

[StefanKarpinski]

Yes, definitely.

[nolta]

• boolean operators: run(test -d $dir&&echo $dir)

Edit: nevermind, i should just write success(test -d $dir) && run(echo $dir)

[StefanKarpinski]

Yep. The former can't actually work because && and || are control flow constructs, not operators.

[Keno]

This all works now:

julia> using Base.FS

julia> readall("test.julia")
could not open file test.julia
 in open at io.jl:277
 in open at io.jl:297
 in readall at io.jl:424

julia> open("test.julia",JL_O_WRONLY|JL_O_CREAT,0o644)
File("test.julia",true,11)

julia> fh=ans
File("test.julia",true,11)

julia> run(`echo Hello`>fh)
true

julia> close(fh)
File("test.julia",false,-1)

julia> run(`echo World`>>"test.julia")
true

julia> run("test.julia">`tee`)
Hello
World
true

julia> pipe=write_to(`tee`>STDOUT)[1]
NamedPipe(connected,0 bytes waiting)

julia> write(pipe,"Test\n")
no method write(NamedPipe,ASCIIString)

julia> print(pipe,"Test\n")

Test
julia> run(`doesnotexist`)
execvp(): No such file or directory
failed process: Process(`doesnotexist`, ProcessExited(-1)) [-1]
 in pipeline_error at process.jl:385
 in run at process.jl:374

julia> success(`false`)
false

julia> success(`true`)
true

julia> success(`echo DONT PRINT THIS`)
true

[aviks]

Are the open() functions in base/io.jl now deprecated?

[Keno]

No, but they will be soon (i.e. as soon as I'm done writing the new one). We're moving to an all-libuv stack for I/O. The great thing about the module system is that i can just develop this one without ever touching the old one and when it's ready write import Base.open, etc., delete io.jl and be done with it.