This question already has answers here:
How to save both matching and non-matching from grep
(3 answers)
Closed 1 year ago.
Currently My shell script iterate the lines in one huge file two times:
(What I want to do is just like the shell script below.)
grep 'some_text' huge_file.txt > lines_contains_a.txt
grep -v 'some_text' huge_file.txt > lines_not_contains_a.txt
but it is slow.
How to do the same thing only iterate the lines once?
Thanks!
With GNU awk:
awk '/some_text/ { print >> "lines_contains_a.txt" }
!/some_text/ { print >> "lines_not_contains_a.txt" }' huge_file.txt
With sed:
sed -n '/some_text/ w lines_contains_a.txt
/some_text/! w lines_not_contains_a.txt' huge_file.txt
Related
This question already has answers here:
How can I view only the first n lines of the file?
(2 answers)
Closed 4 years ago.
I am working on ARM-based processor and I am preparing inside it a shell script that writes into a text file a set of commands output.
I want it to write exactly 10 lines of a command's output (for example top command) but I don't know how, would you help me please ?
Thank you.
Which operating system are you working in ? If you have awk installed, you
can do:
command | awk 'NR<=10' > f.txt
command | head -n 10 > file.txt
If you want a pure Bash solution:
n=0
command | while (( n++ != 10 )) && IFS= read -r line; do
printf '%s\n' "$line"
done
command | sed 1,10p > f.txt
sed filters lines based on a pattern and performs an action on them. In this case, pattern is to filter lines whose number is between 1 and 10, and action is just to 'p'rint them.
This question already has answers here:
Can grep show only words that match search pattern?
(15 answers)
Closed 5 years ago.
I have a requirement of searching a pattern like x=<followed by any values> from a file and displaying the pattern i.e x=<followed by any values>, only in the screen, not the whole line. How can I do it in Linux?
I have 3 answers, from simple (but with caveats) to complex (but foolproof):
1) If your pattern never appears more than once per line, you could do this (assuming your shell is
PATTERN="x="
sed "s/.*\($PATTERN\).*/\1/g" your_file | grep "$PATTERN"
2) If your pattern can appear more than once per line, it's a bit harder. One easy but hacky way to do this is to use a special characters that will not appear on any line that has your pattern, eg, "#":
PATTERN="x="
SPECIAL="#"
grep "$PATTERN" your_file | sed "s/$PATTERN/$SPECIAL/g" \
| sed "s/[^$SPECIAL]//g" | sed "s/$SPECIAL/$PATTERN/g"
(This won't separate the output pattern per line, eg. you'll see x=x=x= if a source line had 3 times "x=", this is easy to fix by adding a space in the last sed)
3) Something that always works no matter what:
PATTERN="x="
awk "NF>1{for(i=1;i<NF;i++) printf FS; print \"\"}" \
FS="$PATTERN" your_file
This question already has answers here:
how to read file from line x to the end of a file in bash
(7 answers)
Closed 7 years ago.
For example, I have a file
1
2
3
then I want to output from 2nd row to tail
How can I do it in linux
tail -n+2 my_file
will output all the lines in myfile starting with line 2. (-n2 would show you the last two lines.)
tail has lots more options. Type man tail for complete documentation.
shorter with
$ sed 1d filename
or with awk
$ awk 'NR>1' filename
This question already has answers here:
What's the opposite of head? I want all but the first N lines of a file
(9 answers)
Closed 8 years ago.
I have a program that displays many line in the output
How I can make it display the all output except the first 2 lines?
easily using tail command:
tail -n+3
You could use awk
awk 'NR>2' file
In order to complete the triplet,
sed '1,2d' file
This question already has answers here:
how can I combine these lines
(4 answers)
Closed 8 years ago.
I want convert this text on a given file:
87665
S
3243423
S
334243
N
...
to something like this:
87665,S
3243423,S
334243,N
...
I've been reading some similar questions, but it didn't work... is there a way to do this with a single line command in linux?
Thanks!
Using sed:
sed '$!N;s/\n/,/' filename
Using paste:
paste -d, - - < filename
paste would leave a trailing , in case the input has an odd number of lines.
Something like this might work for you:
$ awk 'NR%2{a=$0;next}{print a","$0}' file
87665,S
3243423,S
334243,N
To handle files with odd lines, you can do:
awk '{printf "%s%s", $0, NR%2?",":ORS}' file
Just for fun, a pure bash solution:
while IFS= read -r l1; do
read -r l2
printf '%s\n' "$l1${l2:+,$l2}"
done < file
If there's an odd number of lines, the last line will not have a trailing comma.