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bashcygwin

Cygwin cigstart and mintty not writing tail -f piped to grep to file

I'm trying to create a .sh file that runs a process and then writes some of the logging output to a separate file. I have pretty much everything working except for a way to get cygwin to actually write to the file. Both of the following display a new cygwin window and seem to follow the log file but neither write to the output file:

cygstart tail -f ./logs/full-log.txt | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt
mintty tail -f ./logs/full-log.txt | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt

The following works, but I would like to incorporate this into my larger script so I need someway of getting it to run in the background so my script can continue on.

tail -f ./logs/full-log.txt | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt
Solution

  • I suspect that

    cygstart tail -f ./logs/full-log.txt | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt

    means:

    { cygstart tail -f ./logs/full-log.txt; } | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt

    i.e. you're running:

    { cygstart tail } | grep

    instead of what you're trying to do:

    cygstart { tail  | grep }

    If you're just trying to modify a shell script to put tail | grep in the background then this is probably all you really need:

    ( tail -f ./logs/full-log.txt | grep --line-buffered "LOG_FILE:" > ./logs/lrp-log.txt; ) &