It copys one specified file to multiple "unique"(filter those different pathnames which in fact point to the same physical path) paths with parallelism in bash. In contrast to sequential copy processes, it performs well under multiprocessor systems.
The efficiency of Co-process is normally determined by three factors:
1.Whether CPU bound or not
2.Whether scientific data processing or not
3.Whether I/O or not
Code:
#!/bin/sh
#
# Written by home_king <home_king@163.com>
# mcp---Multiple copy with Co-Process
# command format:
# mcp filename pathname1 pathname2 ... pathnameN
#
checkargs(){
if [ $# -eq 0 ];then
echo 'No arguments supplied!'
return 1
fi
cpfile=$1
if [ ! -f $cpfile ]; then
echo 'Invaild file to copy!'
return 1
fi
shift
for tmparg in "$@"; do
if [ ! -d $tmparg ];then
echo "There's at least one invalid directory"
return 1
fi
done
argnums=($(echo $(stat -Lc %i $@) | awk -v inum=$(stat -c %i $PWD) '{for(i=1;i<=NF;i++){if($i == inum)continue;ldirs[$i]=i}} END{for(item in ldirs){print ldirs[item]}}'))
}
checkargs $@
[ $? -eq 0 ] || exit 1
shift
echo "Destination:"
for arg in "${argnums[@]}"; do
eval echo '$'$arg
eval cp -f $cpfile '$'$arg &
done
wait
echo ""
echo 'All done!'
Originally posted by home_king Well, it's the typical way to make "co-process" in Bash, isn't it?
Well no, not at all. Here is the bash FAQ which is being maintained by the author of bash. According to bash's author, the recommended technique is "named pipe pairs (one for read, one for write)". Naturally, there would also be a process connected to the named pipes.
Originally posted by Perderabo Well no, not at all. Here is the bash FAQ which is being maintained by the author of bash. According to bash's author, the recommended technique is "named pipe pairs (one for read, one for write)". Naturally, there would also be a process connected to the named pipes.
It is never said that "daemon+wait" is the only way to make "Co-process" in Bash, but the typical way.
What's more, conceptly, "named pipe" is different from "Co-process". The former depends some command's position parameters. Strictly speaking, it is called "Process Substitution".
Have a look at my example:
Code:
tar cf >(gzip -v9cf >dir.tar.gz) dir/
This commnad bound the input of gzip process with the first parameter(also tar's output destination) of tar process.
Another example:
Code:
cmp <(cat file1) <(cat file2)
It's not "Co-process"!
It's not the case that "named pipe pair"! The number of named pipes is restricted by the number of appropriate position parameters.
Please refer to ¡¶Learning the bash shell¡·of O'reilly.
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04-18-2004
