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Top Forums UNIX for Beginners Questions & Answers Shell script to tail a file with unknown numbers Post 303038721 by apmcd47 on Thursday 12th of September 2019 06:52:30 AM
Old 09-12-2019
Assuming GNU tail you can either list lines from the end (--lines=1234) or from the beginning (--lines=+1234) of the file. Thus listing the full file could be done with
Code:
tail --lines=+1 myfile

In your script you could have a variable nlines which could contain the value 100000, 200000 or +1 and could be used thus:
Code:
tail --lines=$nlines $logfile

The best way to get the values into your script would be to use getopts as in
Code:
while getopts lhf name
do
   case $name in
   l) nlines=100000 ;;
   h) nlines=200000 ;;
   f) nlines=+1 ;;
   esac
done
shift $(( OPTIND - 1))

The log files could be added to the end of the argument list or with more option switches using getopts (use the bash help facility for more info).

Andrew
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SCRIPT(1)						    BSD General Commands Manual 						 SCRIPT(1)

NAME
script -- make typescript of terminal session SYNOPSIS
script [-adfpqr] [-c command] [file] DESCRIPTION
script makes a typescript of everything printed on your terminal. It is useful for students who need a hardcopy record of an interactive session as proof of an assignment, as the typescript file can be printed out later with lpr(1). If the argument file is given, script saves all dialogue in file. If no file name is given, the typescript is saved in the file typescript. Option: -a Append the output to file or typescript, retaining the prior contents. -c command Run the named command instead of the shell. Useful for capturing the output of a program that behaves differently when associated with a tty. -d When playing back a session with the -p flag, don't sleep between records when playing back a timestamped session. -f Flush output after each write. This is useful for watching the script output in real time. -p Play back a session recorded with the -r flag in real time. -q Be quiet, and don't output started and ended lines. -r Record a session with input, output, and timestamping. The script ends when the forked shell exits (a control-D to exit the Bourne shell (sh(1)), and exit, logout or control-d (if ignoreeof is not set) for the C-shell, csh(1)). Certain interactive commands, such as vi(1), create garbage in the typescript file. script works best with commands that do not manipulate the screen, the results are meant to emulate a hardcopy terminal. ENVIRONMENT
The following environment variable is used by script: SHELL If the variable SHELL exists, the shell forked by script will be that shell. If SHELL is not set, the Bourne shell is assumed. (Most shells set this variable automatically). SEE ALSO
csh(1) (for the history mechanism). HISTORY
The script command appeared in 3.0BSD. BUGS
script places everything in the log file, including linefeeds and backspaces. This is not what the naive user expects. BSD
October 17, 2009 BSD
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