I'm trying to unzip a file and redirect the output to a named pipe and another file. Therefore I'm using the command tee.
gunzip -c $FILE | tee -a $UNZIPPED_FILE > $PIPE
My question is is there any other option to achieve the same but with a command that will write the file asynchronously. I want the output redirected to the pipe immediately and that the writing to the file will run in the background by teeing the output to some sort of buffer.
Thanks in advance
What you need is a named pipe (FIFO). First create one:
mkfifo fifo Now we need a process reading from the named pipe. There's an old unix utillity called buffer that was earlier for asynchronous writing to tape devices. Start a process reading from the pipe in the background:
buffer -i fifo -o async_file -u 100000 -t & -i is the input file and -o the output file. The -u flag is only for you to see, that it is really asynchonous. It's a small pause after every write for 1/10 second. And -t gives a summary when finished.
Now start the gunzip process:
gunzip -c archive.gz | tee -a fifo > $OTHER_PIPE You see the gunzip process is ending very fast. In the folder you will see the file async_file growing slowly, that's the background process that is writig to that file, the buffer process. When finishing (can take very long with a huge file) you see a summary. The other file is written directly.
cat fifo > aysnc_file & ?dd, but definitely not with cat. buffer loads everything into shared memory and that's why buffer is not blocking compared to cat.
teeso that the output ofgunzipwill be redirected directly to $PIPE. Therefore I came up with the idea of a buffer that allows this behaviour.