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I want to make a shell script that will effectively grab the last n lines from sterr and stin that were outputted to the console. I have a screen session running a process that will restart it if it crashes via a hacky infinite loop:
#!/bin/bash #This script will be started in a screen session counter=0 while [ $counter -lt 10 ]; do ./run_some_process; last_output=#GRAB PREVIOUS OUTPUT FROM CONSOLE HERE AND LOG TO FILE echo -e "$last_output" >> mylog.txt; sleep 5; #sleep for a few seconds before restarting done What I need is for the 7th line of code to grab the last 10 or so lines from stderr and stdin and append them to a log file
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The tail command, as the name implies, print the last N number of data of the given input. By default it prints the last 10 lines of the specified files.
To look at the last few lines of a file, use the tail command. tail works the same way as head: type tail and the filename to see the last 10 lines of that file, or type tail -number filename to see the last number lines of the file.
Show activity on this post. tail [-F | -f | -r] [-q] [-b number | -c number | -n number] [file ...] -n number : The location is number lines. -f : The -f option causes tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the input.
To display last 20 lines of a file linux use the tail command. Displays the last 20 lines. The default is 10 if you leave out the -n option. Displays the last 100 bytes of the file ( without reguard for the lines).
./run_some_process 2>&1 | tail -10 >>logfle tail -10 will give you last ten lines, 2>&1 redirects stderr to stdout, >>logfle appends to logfile.
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