I have two questions. First, I was wondering how to use sed to remove two header lines or two tail lines. Here I just do the same operation twice...I'm sure there is a better way. Second, and more importantly, is there a better way to have these operations use files other than having it output these dumb ZZ* files and then rm them? There must be a more elegant way...
Thanks!
Mikey
Code:
sed '$d' ZZoutput > ZZoutput1
sed '$d' ZZoutput1 > ZZoutfile
sed '1d' ZZoutfile > ZZoutput2
sed '1d' ZZoutput2 > outfile1
rm ZZ*
I'm not the sed expert, so removing the last two lines is beyond me. Removing the first two lines in one command is pretty straight forward:
Code:
sed '1,2d' <file
1,2d reads: delete the range of lines 1 through 2.
To do everything you want in one swoop, I'd turn to awk:
Code:
awk '
NR > 4 { print buffer1; } # print before overlaying
NR > 2 {
buffer1 = buffer2; # buffer last two lines -- never printed
buffer2 = $0;
}
' <input-file >outputfile
You can smash it all onto one line if you want; easier to read this way I think.
It ditches all lines before line three, then buffers two lines such that the last two lines of the input are never printed.
If you want to replace your original input file, you will have to write the output to a temporary file, and them move the temp file back to the original file name. No way of getting round this, and it does prevent disaster as you can check for errors etc. before renaming the output and trashing the input file.
To answer your other question, you could have piped your commands together to not have to deal with the temp files:
Code:
sed '$d' ZZoutput |sed '$d' | sed '1d' | sed '1d' > outfile1
I didn't test that, so with luck I've not introduced any typos.
Last edited by agama; 08-25-2010 at 12:35 AM..
Reason: added comments
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Hi.
If you have appropriate versions of head and tail, you can use something like:
Code:
#!/usr/bin/env bash
# @(#) s1 Demonstrate head, tail for omitting first, last 2 lines.
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
pl " Versions used:"
head --version | head -1 ; tail --version | head -1
cat >t1 <<EOF
a
b
c
d
e
EOF
pl " Contents of file:"
cat t1
pl " Results of head, then tail:"
head --lines=-2 t1 |
tail --lines=+3
pl " Results of tail, then head:"
tail --lines=+3 t1 |
head --lines=-2
exit 0
producing:
Code:
% ./s1
-----
Versions used:
head (GNU coreutils) 6.10
tail (GNU coreutils) 6.10
-----
Contents of file:
a
b
c
d
e
-----
Results of head, then tail:
c
-----
Results of tail, then head:
c
I have a file called "dsout" with empty rows and duplicate headers.
DATE TIME TOTAL_GB USED_GB %USED
--------- -------- ---------- ---------- ----------
03/05/013 12:34 PM 3151.24316 2331.56653 73.988785 ... (3 Replies)
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Here is the code:
#!... (6 Replies)
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Heya there,
A small selection of my data is shown below.
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### BEGIN ###
Text to remove, contains all kinds of characters
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Hi All,
Following is the part of my script.It does contain many for loops and is not elegant. Please feel free to suggest any changes to make this elegant.
Thanks!
nua7
for i in `ls $CATALINA_HOME/shared/lib/*.jar`;
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I have a data file with over 500,000 records/lines that has the header throughout the file.
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I am running a script (which compares two directory contents) for which I am getting an output of 70 pages in which few pages are blank so I was able to delete those blank lines.
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08-24-2010
