#!/bin/sh -e

# write to output file only after all data from standard input has been read.
# allows to overwrite source files when using shell output redirection.
# example: cat file | grep -v xyz | late-write file

if test 1 -ne $#
then
   echo "arguments: output_file"
fi

a="$(mktemp)"
cat > "$a"
cat "$a" > "$1"
unlink "$a"