I can't tail the last n lines of a file on linux, likewise i can grep
e.g grep "2015-09-29 04:" filename.ext
But how can i combine both such that i display from a certain grep to the end of the file.
You don't use grep or tail any more. You use sed:
sed -n '/^2015-09-29 04:/,$p'
Don't print by default (-n). From the first line starting 2015-09-29 04: to the end of file ($), print the lines.
If you absolutely must use grep and you have GNU grep, then you could consider:
grep -A 999999999 -e '^2015-09-29 04:'
That prints the first billion or so lines after the first line that matches the pattern (and the counter resets if the pattern appears during that trailing material). Of course, if your file is 2 billion lines long and the pattern occurs after a million lines (and never again), then you'll be missing a lot of data.
#!/bin/bash
line_no=`grep -n -m1 "$1" $2 | cut -d: -f1`
echo "Starting at line: " $line_no
tail -n +$line_no $2
Usage: script 'text to hunt for' filename
e.g.
./grep.sh 'Sep 29 13:14' /var/log/syslog
-n issue line numbers
-m1 stop reading after 1 hit
cut out the line number
tail -n +K output lines starting with the Kth
Related
I have a simple question. I am trying to check the 3rd line of multiple files in a folder, so I used this:
head -n 3 MiseqData/result2012/12* | tail -n 1
but this doesn't work obviously, because it only shows the third line of the last file. But I actually want to have last line of every file in the result2012 folder.
Does anyone know how to do that?
Also sorry just another questions, is it also possible to show which file the particular third line belongs to?
like before the third line is shown, is it also possible to show the filename of each of the third line extracted from?
because if I used head or tail command, the filename is also shown.
thank you
With Awk, the variable FNR is the number of the "record" (line, by default) in the current file, so you can simply compare it to 3 to print the third line of each input file:
awk 'FNR == 3' MiseqData/result2012/12*
A more optimized version for long files would skip to the next file on match, since you know there's only that one line where the condition is true:
awk 'FNR == 3 { print; nextfile }' MiseqData/result2012/12*
However, not all Awks support nextfile (but it is also not exclusive to GNU Awk).
A more portable variant using your head and tail solution would be a loop in the shell:
for f in MiseqData/result2012/12*; do head -n 3 "$f" | tail -n 1; done
Or with sed (without GNU extensions, i.e., the -s argument):
for f in MiseqData/result2012/12*; do sed '3q;d' "$f"; done
edit: As for the additional question of how to print the name of each file, you need to explicitly print it for each file yourself, e.g.,
awk 'FNR == 3 { print FILENAME ": " $0; nextfile }' MiseqData/result2012/12*
for f in MiseqData/result2012/12*; do
echo -n `basename "$f"`': '
head -n 3 "$f" | tail -n 1
done
for f in MiseqData/result2012/12*; do
echo -n "$f: "
sed '3q;d' "$f"
done
With GNU sed:
sed -s -n '3p' MiseqData/result2012/12*
or shorter
sed -s '3!d' MiseqData/result2012/12*
From man sed:
-s: consider files as separate rather than as a single continuous long stream.
You can do this:
awk 'FNR==3' MiseqData/result2012/12*
If you like the file name as well:
awk 'FNR==3 {print FILENAME,$0}' MiseqData/result2012/12*
This might work for you (GNU sed & parallel):
parallel -k sed -n '3p\;3q' {} ::: file1 file2 file3
Parallel applies the sed command to each file and returns the results in order.
N.B. All files will only be read upto the 3rd line.
Also,you may be tempted (as I was) to use:
sed -ns '3p;3q' file1 file2 file3
but this will only return the first file.
Hi bro I am answering this question as we know FNR is used to check no of lines so we can run this command to get 3rd line of every file.
awk 'FNR==3' MiseqData/result2012/12*
How do I get the line count of a file from the 2nd line of the file, as the first line is header?
wc -l filename
Is there a way to set some condition into it?
Use the tail command:
tail -n +2 file | wc -l
-n +2 would print the file starting from line 2
You can use awk to count from 2nd line onwards:
awk 'NR>1{c++} END {print c}' file
Or simply use NR variable in the END block:
awk 'END {print NR-1}' file
Alternatively using BASH arithmetic subtract 1 from wc output:
echo $(( $(wc -l < file) -1 ))
Delete first line with GNU sed:
sed '1d' file | wc -l
There is no way to tweak the wc command itself. You should whether process the result of the command, or use another tool.
As suggested in other answers, if you are running Bash, a good way is to put the result of the command into an arithmetic expression like $(( $(command) - 1 )).
In case if you are searching for a portable solution, here is a Perl version:
perl -e '1 while <>; print $. - 1' < file
The variable $. holds the number of lines read since a file handle was last closed. The while loop reads all the lines from the file.
Alternately, you could just subtract 2.
echo $((`cat FILE | wc -l`-2))
Please try this one. It will be solved your problem
$ tail -n +2 filename | wc -l
I have (probably a obvious/stupid) problem:
I want to loop over a list of paths, cut them and use the strings to grep in log files.
While every step works fine on its own and 'processed manually' results in hits - grep does not find anything when in the loop?
for FILE in `awk -F "/" '{print $13}' /tmp/files_not_visible.uniq`; do
echo -e "\n\n$FILE\n";
grep "$FILE" /var/log/PATH/FILENAME-2015.12.*;
done
I also tried to do a while loop as reverse exercise, but fails with the same non-result
while read FILE; do
echo $FILE;
echo $FILE | awk -F "/" '{print $13}' | grep -f - /var/log/PATH/FILENAME-2015.12.* ;
done < /tmp/files_not_visible.uniq/tmp/files_not_visible.uniq
So, I guess there is some systematic issue, how I handle the search string with grep?
Found it: the list of files contained invisible characters as the last character of the line! Probably the user, who send me the list of files, created it on some other OS! And I only copied -of course- the visible characters when testing by hand!
Fixed the loop by cutting the last character of a line with
> sed -e 's/.$//'
In a very large file I need to find the position (line number) of a string, then extract the 2 lines above and below that string.
To do this right now - I launch vi, find the string, note it's line number, exit vi, then use sed to extract the lines surrounding that string.
Is there a way to streamline this process... ideally without having to run vi at all.
Maybe using grep like this:
grep -n -2 your_searched_for_string your_large_text_file
Will give you almost what you expect
-n : tells grep to print the line number
-2 : print 2 additional lines (and the wanted string, of course)
You can do
grep -C 2 yourSearch yourFile
To send it in a file, do
grep -C 2 yourSearch yourFile > result.txt
Use grep -n string file to find the line number without opening the file.
you can use cat -n to display the line numbers and then use awk to get the line number after a grep in order to extract line number:
cat -n FILE | grep WORD | awk '{print $1;}'
although grep already does what you mention if you give -C 2 (above/below 2 lines):
grep -C 2 WORD FILE
You can do it with grep -A and -B options, like this:
grep -B 2 -A 2 "searchstring" | sed 3d
grep will find the line and show two lines of context before and after, later remove the third one with sed.
If you want to automate this, simple you can do a Shell Script. You may try the following:
#!/bin/bash
VAL="your_search_keyword"
NUM1=`grep -n "$VAL" file.txt | cut -f1 -d ':'`
echo $NUM1 #show the line number of the matched keyword
MYNUMUP=$["NUM1"-1] #get above keyword
MYNUMDOWN=$["NUM1"+1] #get below keyword
sed -n "$MYNUMUP"p file.txt #display above keyword
sed -n "$MYNUMDOWN"p file.txt #display below keyword
The plus point of the script is you can change the keyword in VAL variable as you like and execute to get the needed output.
How do I use grep to perform a search which, when a match is found, will print the file name as well as the first n characters in that file? Note that n is a parameter that can be specified and it is irrelevant whether the first n characters actually contains the matching string.
grep -l pattern *.txt |
while read line; do
echo -n "$line: ";
head -c $n "$line";
echo;
done
Change -c to -n if you want to see the first n lines instead of bytes.
You need to pipe the output of grep to sed to accomplish what you want. Here is an example:
grep mypattern *.txt | sed 's/^\([^:]*:.......\).*/\1/'
The number of dots is the number of characters you want to print. Many versions of sed often provide an option, like -r (GNU/Linux) and -E (FreeBSD), that allows you to use modern-style regular expressions. This makes it possible to specify numerically the number of characters you want to print.
N=7
grep mypattern *.txt /dev/null | sed -r "s/^([^:]*:.{$N}).*/\1/"
Note that this solution is a lot more efficient that others propsoed, which invoke multiple processes.
There are few tools that print 'n characters' rather than 'n lines'. Are you sure you really want characters and not lines? The whole thing can perhaps be best done in Perl. As specified (using grep), we can do:
pattern="$1"
shift
n="$2"
shift
grep -l "$pattern" "$#" |
while read file
do
echo "$file:" $(dd if="$file" count=${n}c)
done
The quotes around $file preserve multiple spaces in file names correctly. We can debate the command line usage, currently (assuming the command name is 'ngrep'):
ngrep pattern n [file ...]
I note that #litb used 'head -c $n'; that's neater than the dd command I used. There might be some systems without head (but they'd pretty archaic). I note that the POSIX version of head only supports -n and the number of lines; the -c option is probably a GNU extension.
Two thoughts here:
1) If efficiency was not a concern (like that would ever happen), you could check $status [csh] after running grep on each file. E.g.: (For N characters = 25.)
foreach FILE ( file1 file2 ... fileN )
grep targetToMatch ${FILE} > /dev/null
if ( $status == 0 ) then
echo -n "${FILE}: "
head -c25 ${FILE}
endif
end
2) GNU [FSF] head contains a --verbose [-v] switch. It also offers --null, to accomodate filenames with spaces. And there's '--', to handle filenames like "-c". So you could do:
grep --null -l targetToMatch -- file1 file2 ... fileN |
xargs --null head -v -c25 --