Shell Programming and Scripting

#!/usr/bin/env bash

# @(#) s1	Demonstrate xargs and parallel, succeed with embedded script.

pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
yoohoo() { for _i;do printf "%s" "$_i";done; printf "\n"; }
export -f yoohoo
C=$HOME/bin/context && [ -f $C ] && $C xargs parallel

FILE=${1-data1}

pl " Input file $FILE:"
head $FILE

pl " Results, default:"
cat $FILE |
xargs -L 1

yoohoo
yoohoo " ( Define helper script )"
cat <<"EOF" > s1-helper
#!/usr/bin/env bash
echo " PID = $$; args = $*"
EOF
chmod +x s1-helper
head s1-helper

pl " Results, external script, xargs:"
cat $FILE |
xargs -L 1 ./s1-helper

pl " Results, external script, parallel:"
cat $FILE |
parallel ./s1-helper

pl " Expecting functions to fail."
pe " Why? http://www.perlmonks.org/index.pl?node_id=484296"

pl " Results, function:"
cat $FILE |
xargs yoohoo

pl " Results, function:"
cat $FILE |
parallel yoohoo

exit 0

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
bash GNU bash 3.2.39
xargs (GNU findutils) 4.4.0
parallel GNU parallel 20111122

-----
 Input file data1:
foo
bar
baz

-----
 Results, default:
foo
bar
baz

 ( Define helper script )
#!/usr/bin/env bash
echo " PID = $$; args = $*"

-----
 Results, external script, xargs:
 PID = 12328; args = foo
 PID = 12329; args = bar
 PID = 12330; args = baz

-----
 Results, external script, parallel:
 PID = 12391; args = foo
 PID = 12411; args = bar
 PID = 12431; args = baz

-----
 Expecting functions to fail.
 Why? http://www.perlmonks.org/index.pl?node_id=484296

-----
 Results, function:
xargs: yoohoo: No such file or directory

-----
 Results, function:
yoohoo: Command not found.
yoohoo: Command not found.
yoohoo: Command not found.