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# function zargs {
#
# This function works like GNU xargs, except that instead of reading lines
# of arguments from the standard input, it takes them from the command
# line. This is possible/useful because, especially with recursive glob
# operators, zsh often can construct a command line for a shell function
# that is longer than can be accepted by an external command.
#
# Like xargs, zargs exits with the following status:
# 0 if it succeeds
# 123 if any invocation of the command exited with status 1-125
# 124 if the command exited with status 255
# 125 if the command is killed by a signal
# 126 if the command cannot be run
# 127 if the command is not found
# 1 if some other error occurred.
#
# The full set of GNU xargs options is supported (see help text below);
# although --eof and --max-lines therefore have odd names, they have
# analogous meanings to their xargs counterparts. Also zargs --help is
# a lot more helpful than xargs --help, at least as of xargs 4.1.
#
# Note that "--" is used both to end the options and to begin the command,
# so to specify some options along with an empty set of input-args, one
# must repeat the "--" as TWO consecutive arguments, e.g.:
# zargs --verbose -- -- print There are no input-args
# If there is at least one input-arg, the first "--" may be omitted:
# zargs -p -i one -- print There is just {} input-arg
# Obviously, if there is no command, the second "--" may be omitted:
# zargs -n2 These words will be echoed in five lines of two
#
# BUGS:
#
# In the interests of expediency, numeric options (max-procs, max-lines,
# etc.) are range-checked only when their values make a difference to the
# end result. Because of the way zsh handles variables in math context,
# it's possible to pass the name of a variable as the value of a numeric
# option, and the value of that variable becomes the value of the option.
#
# "Killed by a signal" is determined by the usual shell rule that $? is
# the signal number plus 128, so zargs can be fooled by a command that
# explicitly exits with 129+. Also, zsh prior to 4.1.x returns 1 rather
# than 127 for "command not found" so this function incorrectly returns
# 123 in that case if used with zsh 4.0.x.
#
# With the --max-procs option, zargs may not correctly capture the exit
# status of the backgrounded jobs, because of limitations of the "wait"
# builtin. If the zsh/parameter module is not available, the status is
# NEVER correctly returned, otherwise the status of the longest-running
# job in each batch is captured.
#
# Also because of "wait" limitations, --max-procs spawns max-procs jobs,
# then waits for all of those, then spawns another batch, etc.
#
# Differences from POSIX xargs:
#
# * POSIX requires a space between -I/-L/-n/-s and their numeric argument;
# zargs uses zparseopts, which does not require the space.
#
# * POSIX -L and -n are mutually exclusive and effectively synonymous;
# zargs accepts both and considers -n to be a limit on the total number
# of arguments per command line, that is, including the initial-args.
# Thus the following fails with "argument list too long":
# zargs -n 3 -- echo Here are four words
# The smallest limit implied by the combination of -L and -n is used.
#
# * POSIX implies the last of -n/-i/-I/-l/-L on the command line is meant
# to cancel any of those that precede it. (This is unspecified for
# -I/-L and implementations reportedly differ.) In zargs, -i/-I have
# this behavior, as do -l/-L, but when -i/-I appear anywhere then -l/-L
# are ignored (forced to 1).
emulate -L zsh || return 1
local -a opts eof n s l P i
local ZARGS_VERSION="1.4"
if zparseopts -a opts -D -- \
-eof::=eof e::=eof \
-exit x \
-help \
-interactive p \
-max-args:=n n:=n \
-max-chars:=s s:=s \
-max-lines::=l l::=l L:=l \
-max-procs:=P P:=P \
-no-run-if-empty r \
-null 0 \
-replace::=i i::=i I:=i \
-verbose t \
-version
then
if (( $opts[(I)--version] ))
then
print -u2 zargs version $ZARGS_VERSION zsh $ZSH_VERSION
fi
if (( $opts[(I)--help] ))
then
>&2 <<-\HELP
Usage: zargs [options --] [input-args] [-- command [initial-args]]
If command and initial-args are omitted, "print -r --" is used.
Options:
--eof[=eof-str], -e[eof-str]
Change the end-of-input-args string from "--" to eof-str. If
given as --eof=, an empty argument is the end; as --eof or -e,
with no (or an empty) eof-str, all arguments are input-args.
--exit, -x
Exit if the size (see --max-chars) is exceeded.
--help
Print this summary and exit.
--interactive, -p
Prompt before executing each command line.
--max-args=max-args, -n max-args
Use at most max-args arguments per command line.
--max-chars=max-chars, -s max-chars
Use at most max-chars characters per command line.
--max-lines[=max-lines], -l[max-lines]
Use at most max-lines of the input-args per command line.
This option is misnamed for xargs compatibility.
--max-procs=max-procs, -P max-procs
Run up to max-procs command lines in the background at once.
--no-run-if-empty, -r
Do nothing if there are no input arguments before the eof-str.
--null, -0
Split each input-arg at null bytes, for xargs compatibility.
--replace[=replace-str], -i[replace-str]
Substitute replace-str in the initial-args by each initial-arg.
Implies --exit --max-lines=1.
--verbose, -t
Print each command line to stderr before executing it.
--version
Print the version number of zargs and exit.
HELP
return 0
fi
if (( $opts[(I)--version] ))
then
return 0
fi
if (( $#i ))
then
l=1
i=${${${i##-(i|I|-replace(=|))}[-1]}:-\{\}}
opts[(r)-x]=-x
# The following is not how xargs is documented,
# but GNU xargs does behave as if -i implies -r.
opts[(r)-r]=-r
fi
if (( $#P ))
then
P=${${P##-(P|-max-procs(=|))}:-1}
if [[ x${P} != x$[P] ]]
then
print -u2 zargs: invalid number for -P option
return 1
fi
else P=1
fi
else
return 1
fi
local -i end c=0
if [[ $eof == -(e|-eof) ]]; then ((end=ARGC+1))
elif (( $#eof )); then end=$argv[(i)${eof##-(e|-eof=)}]
else end=$argv[(i)--]
fi
local -a args call command; command=( ${argv[end+1,-1]} )
if (( $opts[(I)-(null|0)] ))
then set -- ${(ps:\000:)argv[1,end-1]}
else set -- $argv[1,end-1]
fi
if [[ -n $command ]]
then (( c = $#command - 1 ))
else command=( print -r -- )
fi
local wait bg
local execute='
if (( $opts[(I)-(-interactive|p)] ))
then read -q "?$call?..." || continue
elif (( $opts[(I)-(-verbose|t)] ))
then print -u2 -r -- "$call"
fi
eval "{
\$call
} $bg"'
local ret=0 analyze='
case $? in
(0) ;;
(<1-125>|128) ret=123;;
(255) return 124;;
(<129-254>) return 125;;
(126) return 126;;
(127) return 127;;
(*) return 1;;
esac'
if (( ARGC == 0 ))
then
if (( $opts[(I)-(-no-run-if-empty|r)] ))
then return 0
else
call=($command)
# Use "repeat" here so "continue" won't complain.
repeat 1 eval "$execute ; $analyze"
return $ret
fi
fi
n=${${n##-(n|-max-args(=|))}:-$[ARGC+c]}
if (( n <= 0 ))
then
print -u2 'zargs: value for max-args must be >= 1'
return 1
fi
if (( n > c ))
then (( n -= c ))
else
print -u2 zargs: argument list too long
return 1
fi
s=${${s##-(s|-max-chars(=|))}:-20480}
if (( s <= 0 ))
then
print -u2 'zargs: value for max-chars must be >= 1'
return 1
fi
l=${${${l##*-(l|L|-max-lines(=|))}[-1]}:-${${l[1]:+1}:-$ARGC}}
if (( l <= 0 ))
then
print -u2 'zargs: value for max-lines must be >= 1'
return 1
fi
P=${${P##-(P|-max-procs(=|))}:-1}
if (( P < 0 ))
then
print -u2 'zargs: value for max-procs must be >= 0'
return 1
fi
if (( P != 1 && ARGC > 1 ))
then
# These setopts are necessary for "wait" on multiple jobs to work.
setopt nonotify nomonitor
bg='&'
if zmodload -i zsh/parameter 2>/dev/null
then
wait='wait %${(k)^jobstates[(R)running:*]}'
else
wait='wait'
fi
fi
# Everything has to be in a subshell just in case of backgrounding jobs,
# so that we don't unintentionally "wait" for jobs of the parent shell.
(
while ((ARGC))
do
if (( P == 0 || P > ARGC ))
then (( P = ARGC ))
fi
repeat $P
do
((ARGC)) || break
for (( end=l; end && ${(c)#argv[1,end]} > s; end/=2 )) :
(( end > n && ( end = n ) ))
args=( $argv[1,end] )
shift $((end > ARGC ? ARGC : end))
if (( $#i ))
then call=( ${command/$i/$args} )
else call=( $command $args )
fi
if (( ${(c)#call} > s ))
then
print -u2 zargs: cannot fit single argument within size limit
# GNU xargs exits here whether or not -x,
# but that just makes the option useless.
(( $opts[(I)-(-exit|x)] )) && return 1
continue
else
eval "$execute"
fi
done
eval "$wait
$analyze"
done
return $ret
)
# }
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