280-pipes-manual.oh

#!/usr/bin/env oh

# KEYWORD: manual
# PROVIDE: pipes
# REQUIRE: external

## ### Pipes
##
## Using oh, it is relatively simple to record the exit status for each stage
## in a pipeline. The example below,
##
#{
define exit-status: map

define pipe-fitting: method (label cmd: args) = {
    exit-status::set label: cmd @args
}

pipe-fitting "1st" echo 1 2 3 |
pipe-fitting "2nd" tr " " "\n" |
pipe-fitting "3rd" grep 2

echo "1st stage exit status =>": exit-status::get "1st"
echo "2nd stage exit status =>": exit-status::get "2nd"
echo "3rd stage exit status =>": exit-status::get "3rd"
#}
##
## produces the output,
##
#+     2
#+     1st stage exit status => true
#+     2nd stage exit status => 0
#+     3rd stage exit status => 0
##