Short definition: grep: search for specific terms in a file #usage $ grep This file.txt Every line containing “This” Every line containing “This” Every line containing “This” Every line containing “This” $ cat file.txt Every line containing “This” Every line containing “This” Every line containing “That” Every line containing “This” Every line containing “This” Now … Read more
Use awk with a flag to trigger the print when necessary: $ awk ‘/abc/{flag=1;next}/mno/{flag=0}flag’ file def1 ghi1 jkl1 def2 ghi2 jkl2 How does this work? /abc/ matches lines having this text, as well as /mno/ does. /abc/{flag=1;next} sets the flag when the text abc is found. Then, it skips the line. /mno/{flag=0} unsets the flag … Read more
In GNU Awk 4.1.0 (released 2013) and later, it has the option of “inplace” file editing: […] The “inplace” extension, built using the new facility, can be used to simulate the GNU “sed -i” feature. […] Example usage: $ gawk -i inplace ‘{ gsub(/foo/, “bar”) }; { print }’ file1 file2 file3 To keep the … Read more
ts from moreutils will prepend a timestamp to every line of input you give it. You can format it using strftime too. $ echo ‘foo bar baz’ | ts Mar 21 18:07:28 foo bar baz $ echo ‘blah blah blah’ | ts ‘%F %T’ 2012-03-21 18:07:30 blah blah blah $ To install it: sudo apt-get … Read more
perl -pe ‘chomp if eof’ filename >filename2 or, to edit the file in place: perl -pi -e ‘chomp if eof’ filename [Editor’s note: -pi -e was originally -pie, but, as noted by several commenters and explained by @hvd, the latter doesn’t work.] This was described as a ‘perl blasphemy’ on the awk website I saw. … Read more
You don’t see anything, because of buffering. The output is shown, when there are enough lines or end of file is reached. tail -f means wait for more input, but there are no more lines in file and so the pipe to grep is never closed. If you omit -f from tail the output is … Read more
awk ‘!seen[$0]++’ file.txt seen is an associative array that AWK will pass every line of the file to. If a line isn’t in the array then seen[$0] will evaluate to false. The ! is the logical NOT operator and will invert the false to true. AWK will print the lines where the expression evaluates to … Read more
Answer cat testfile | awk ‘{ print length, $0 }’ | sort -n -s | cut -d” ” -f2- Or, to do your original (perhaps unintentional) sub-sorting of any equal-length lines: cat testfile | awk ‘{ print length, $0 }’ | sort -n | cut -d” ” -f2- In both cases, we have solved your … Read more
awk ‘{print $(NF-1)}’ Should work
paste is good for this job: paste -d ” ” – – < filename