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#!/bin/sh

# split data from stdin to multiple invocations of a command

# without creating temporary files

# Author:

# http://www.pixelbeat.org/

# Notes:

# This script may be useful for chunking a stream before

# sending to an FTP server supporting limited file sizes for e.g.

# Using `ifne` from moreutils is not possible as it consumes BUFSIZ,

# and doesn't indicate when no more data is available. I.E. it's good

# for conditional _single_ invocations of a command only.

# Changes:

# V0.1, 29 Nov 2010, Initial release

# http://github.com/pixelb/scripts/commits/master/scripts/split_to

if [ "$#" -lt 1 ]; then

me=$(basename $0)

echo "Usage: $me size [-n] [command]" >&2

echo "split data from stdin to multiple invocations of a command" >&2

echo >&2

echo " -n pass the chunk number as the first parameter to command" >&2

echo "Examples:" >&2

echo " $0 10000 'wc -c' < /bin/ls" >&2

echo " $0 10000 < /bin/ls" >&2

echo " $0 10000 -n < /bin/ls" >&2

exit 1

fi

chunk_size=$1; shift

test "$1" = -n && { pass_part=1; shift; }

test "$1" && cmd="$*" || cmd=example_cmd

example_cmd() { echo "processing part $1 ($(wc -c) bytes)"; }

part=1

while true; do

c=$(od -to1 -An -N1) # getc

test "$c" || break

c=$(echo $c) # trim

test "$pass_part" && ppart=$part

{

printf "\\$c" # ungetc

head -c$(($chunk_size-1))

} | $cmd $ppart || break

part=$(($part+1))

done