Opposite of tail: all lines except the last n lines

headsolaristailunixunix-utils

How can I discard the last n lines of a file with a unix command line filter?

That would be sort of the opposite of tail: tail discards the first n lines but pipes the rest through, but I want the command to pipe everything through except the last n lines.

Unfortunately I haven't found anything like that – head doesnt help, too. EDIT: At least in Solaris it does not take negative arguments.

Update: I'm mostly interested in a solution that works for big files, i.e. logfiles, where you might want to inspect what happened except in the last minutes.

Best Answer

If you have GNU head, you can use

head -n -5 file.txt

to print all but the last 5 lines of file.txt.

If head -n takes no negative arguments, try

head -n $(( $(wc -l file.txt | awk '{print $1}') - 5 )) file.txt

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Tail/head all line except X last/first Lines

tail -n+3 outputs the last lines starting from the third one.

Linux – how to tail into the last file on a remote server via ssh

When your alias runs ssh ... "cd ...; commands using backquote that I can't easily show on Stack" that commands your shell to run the backquoted ls ... | ... pipeline locally, which finds the name of the newest file in your current directory on your system, and sends that filename as part of the command to the remote system, where of course trying to tail that file doesn't work.

Your options are:

 # ugly quoting to work with doublequotes
 alias logger='ssh ... "cd ...; tail -f \`ls ... | ...\`; bash --login"'

 # shell function or script, which let you use clearer singlequotes 
 logger(){
   ssh ... 'cd ...; tail -f `ls ... | ...`; bash --login'
 }
 # or 
 cat <<"END" >logger # use some dir (early) in $PATH 
 ssh ... 'cd ...; tail -f `ls ... | ...`; bash --login' 
 END
 chmod +x logger

In general you could also provide the command as input to the remote shell instead of a commandline (argument)

ssh ... <<"END" # shouldn't need -t in this case 
cd ...; tail -f `ls ... | ...`
END

but this doesn't combine with your apparent though unmentioned and unexplained desire to leave bash --login running after exiting the tail.

Note the two heredoc cases quote the delimiter string so local shell does NOT subsitute backquote, or certain other things, within the data.

And in all cases it would be better to use the newer $( ... ) syntax for command substitution instead of the old backquote syntax -- especially for questions on Stack where backquotes interfere with (much? most?) non-codeblock formatting.

Best Answer

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Tail/head all line except X last/first Lines

Linux – how to tail into the last file on a remote server via ssh

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