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

CodePudding user response：

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; ) &