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Full Discussion: Delete the last line in a file using AWK or PERL
Top Forums Shell Programming and Scripting Delete the last line in a file using AWK or PERL Post 302088031 by suman_jakkula on Friday 8th of September 2006 05:32:34 AM
Old 09-08-2006
Not home work. Requirement in my work.
I could do it using some other utilities. I heard awk is much powelful utility for file processing. Thought it would improve runtime performance.

I tried 2 possibilities

Using Sed :
lastLine=`wc -l <filename> | awk '{ print $1 }'`
sed -e "`echo $lastLine`d" <filename>

Using head :
lastLine=`wc -l <filename> | awk '{ print $1 }'`
head -`echo "$lineNo - 1" | bc` <filename>
Sed version was better in terms of time of execution.
Any better way to do this?

Regards,
----------
Suman
 

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LEARN ABOUT REDHAT

largefile

largefile(5)                                            Standards, Environments, and Macros                                           largefile(5)

NAME

       largefile - large file status of utilities

DESCRIPTION

       A  large file is a regular file whose size is greater than or equal to 2 Gbyte ( 2**31 bytes). A small file is a regular file whose size is
       less than 2 Gbyte.

   Large file aware utilities
       A utility is called large file aware if it can process large files in the same manner as it does small files. A utility that is large  file
       aware is able to handle large files as input and generate as output large files that are being processed. The exception is where additional
       files  are used as system configuration files or support files that can augment the processing. For example, the file utility supports  the
       -m  option  for  an  alternative "magic" file and the -f option for a support file that can contain a list of file names. It is unspecified
       whether a utility that is large file aware will accept configuration or support files that are large files. If a large file  aware  utility
       does  not accept configuration or support files that are large files, it will cause no data loss or corruption upon encountering such files
       and will return an appropriate error.

       The following /usr/bin utilities are large file aware:

       adb           awk           bdiff         cat           chgrp
       chmod         chown         cksum         cmp           compress
       cp            csh           csplit        cut           dd
       dircmp        du            egrep         fgrep         file
       find          ftp           getconf       grep          gzip
       head          join          jsh           ksh           ln
       ls            mdb           mkdir         mkfifo        more
       mv            nawk          page          paste         pathchck
       pg            rcp           remsh         rksh          rm
       rmdir         rsh           sed           sh            sort
       split         sum           tail          tar           tee
       test          touch         tr            uncompress    uudecode
       uuencode      wc            zcat

       The following /usr/xpg4/bin utilities are large file aware:

       awk           cp            chgrp         chown         du
       egrep         fgrep         file          grep          ln
       ls            more          mv            rm            sed
       sh            sort          tail          tr

       The following /usr/xpg6/bin utilities are large file aware:

       getconf       ls            tr

       The following /usr/sbin utilities are large file aware:

       install       mkfile        mknod         mvdir         swap

       See the USAGE section of the swap(1M) manual page for limitations of swap on block devices greater than 2 Gbyte on a 32-bit operating  sys-
       tem.

       The following /usr/ucb utilities are large file aware:

       chown         from          ln            ls            sed
       sum           touch

       The /usr/bin/cpio and /usr/bin/pax utilities are large file aware, but cannot archive a file whose size exceeds 8 Gbyte - 1 byte.

       The /usr/bin/truss utilities has been modified to read a dump file and display information relevant to large files, such as offsets.

   cachefs file systems
       The following /usr/bin utilities are large file aware for cachefs file systems:

       cachefspack      cachefsstat

       The following /usr/sbin utilities are large file aware for cachefs file systems:

       cachefslog       cachefswssize   cfsadmin         fsck
       mount            umount

   nfs file systems
       The following utilities are large file aware for nfs file systems:

       /usr/lib/autofs/automountd    /usr/sbin/mount
       /usr/lib/nfs/rquotad

   ufs file systems
       The following /usr/bin utility is large file aware for ufs file systems:

              df

       The following /usr/lib/nfs utility is large file aware for ufs file systems:

              rquotad

       The following /usr/xpg4/bin utility is large file aware for ufs file systems:

              df

       The following /usr/sbin utilities are large file aware for ufs file systems:

       clri          dcopy         edquota       ff            fsck
       fsdb          fsirand       fstyp         labelit       lockfs
       mkfs          mount         ncheck        newfs         quot
       quota         quotacheck    quotaoff      quotaon       repquota
       tunefs        ufsdump       ufsrestore    umount

   Large file safe utilities
       A  utility  is called large file safe if it causes no data loss or corruption when it encounters a large file. A utility that is large file
       safe is unable to process properly a large file, but returns an appropriate error.

       The following /usr/bin utilities are large file safe:

       audioconvert     audioplay    audiorecord    comm          diff
       diff3            diffmk       ed             lp            mail

       mailcompat       mailstats    mailx          pack          pcat
       red              rmail        sdiff          unpack        vi
       view

       The following /usr/xpg4/bin utilities are large file safe:

       ed            vi            view

       The following /usr/xpg6/bin utility is large file safe:

       ed

       The following /usr/sbin utilities are large file safe:

       lpfilter      lpforms

       The following /usr/ucb utilities are large file safe:

       Mail          lpr

       The following /usr/lib utility is large file safe:

              sendmail

SEE ALSO

       lf64(5), lfcompile(5), lfcompile64(5)

SunOS 5.10                                                          7 Nov 2003                                                        largefile(5)
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