I am a windows user having basic idea about LINUX and i encountered this command:
cat countryInfo.txt | grep -v "^#" >countryInfo-n.txt
After some research i found that cat is for concatenation and grep is for regular exp search (don't know if i am right) but what will the above command result in (since both are combined together) ?
Thanks in Advance.
EDIT: I am asking this as i dont have linux installed. Else, i could test it.
Short answer: it removes all lines starting with a # and stores the result in countryInfo-n.txt.
Long explanation:
cat countryInfo.txt reads the file countryInfo.txt and streams its content to standard output.
| connects the output of the left command with the input of the right command (so the right command can read what the left command prints).
grep -v "^#" returns all lines that do not (-v) match the regex ^# (which means: line starts with #).
Finally, >countryInfo-n.txt stores the output of grep into the specified file.
It will remove all lines starting with # and put the output in countryInfo-n.txt
This command would result in removing lines starting with # from the file countryInfo.txt and place the output in the file countryInfo-n.txt.
This command could also have been written as
grep -v "^#" countryInfo.txt > countryInfo-n.txt
See Useless Use of Cat.
Related
I want to make a simple dmenu command that reads a file of commands and names. Then takes the names and displays them using dmenu then takes dmenu's output and runs the associated command using the file again.
I got to the point where dmenu displays the names, but I don't really know where to go from there. Learning bash is a really daunting task to me and I don't really know where to start with this seemingly simple script/command.
here is the file:
Pushbullet
google-chrome-stable --app=https://www.pushbullet.com
Steam
steam
Chrome
google-chrome-stable
Libre Office
libreoffice
Transmission
transmission-qt
Audio Control Panel
sudo pavucontrol & bluberry
and here is what I have so far for my command:
awk 'NR % 2 != 0' /home/rocco/programlist | dmenu | ??(grep -l "stdout" /home/rocco/programlist....)
It was my thinking that I could somehow pipe into grep or awk with the name of the application then get the line number then add one and pipe that into sh.
Thanks
I have no experience with dmenu but if I understand how it works correctly, this should do what you want. Wrapping a command in $(…) returns the output as a variable, which we can pass on to another command.
#!/bin/bash
plist="/home/rocco/programlist"
# pipe every second line to dmenu
selected=$(awk 'NR % 2 != 0' "$plist" | dmenu)
# search for the selected item, get the command after it
cmd=$(grep -A1 "$selected" "$plist" | tail -n 1)
# run the command
$cmd
Worth mentioning a mistake in your question. dmenu sends to stdout, or standard output, but the next program in line would be reading stdin, or standard input. In any case, grep can't take patterns on standard input, which is why I've saved to a variable instead of trying to pipe it somewhere.
Assuming you have programlist.txt in the working directory you can use:
awk 'NR%2 !=0' programlist.txt |dmenu |awk '{system("grep --no-group-separator -A 1 '"'"'"$0"'"'"' programlist.txt");}' |awk '{if(NR==2){system($0);}}'
Note the quoting of the $0 in the first awk envocation. This is necessary to get names with spaces in them like "Libre Office"
I'm trying to figure out how to efficiently copy-paste from X application to the terminal. Specifically I want to highlight a text section in my web browser, then paste this commented to a file after the shebang line.
the code I have so far is this:
xclip -o | sed 's/^/#/' | sed '2n' myscript.pl
the first command takes the text that I have highlighted in my browser
the second command comments the lines by adding #
the last bit does not work..
what I am trying to do here is append the text after line number 2 to my script. But obviously I am doing this wrong.. Does anyone have a helpful suggestion?
You can use sed read for safely handling all types of input, including input with special characters and multiple lines. This requires an intermediate file:
xclip -o | sed -e 's/^/#/g' -e '$s/$/\n/' > TMP && sed -i '1r TMP' den && rm TMP
sed only operates on one input stream (either a pipe or a file), if you are using the output of xclip as the data stream then you can't also tell sed to read from a file. Instead you could use command substitution to store the modified output, and use that in a separate command. How about:
sed "2i$(xclip -o | sed 's/^/#/')" myscript.pl
This will print the amended file to stdout, if you want to edit the file itself then use the -i flag.
I am working on a Java EE application where its logs will be generated inside a Linux server .
I have used the command tail -f -n -10000 MyLog
It displayed last 1000 lines from that log file .
Now I pressed Ctrl + c in Putty to disconnect the logs updation ( as i am feared it may be updated with new requests and I will loose my data )
In the displayed result, how can I search for a particular keyword ?? (Used / String name to search but it's not working)
Pipe your output to PAGER.
tail -f -n LINE_CNT LOG_FILE | less
then you can use
/SEARCH_STRING
Two ways:
tail -n 10000 MyLog| grep -i "search phrase"
tail -f -n 10000 MyLog | less
The 2nd method will allow you to search with /. It will only search down but you can press g to go back to the top.
Edit: On testing it seems method 2 doesn't work all that well... if you hit the end of the file it will freeze till you ctrl+c the tail command.
You need to redirect the output from tail into a search utility (e.g. grep). You could do this in two steps: save the output to a file, then search in the file; or in one go: pipe the ouput to the search utility
To see what goes into the file (so you can hit Ctlr+c) you can use the tee command, which duplicates the output to the screen and to a file:
tail -f -n -10000 MyLog | tee <filename>
Then search within the file.
If you want to pipe the result into the search utility, you can use the same trick as above, but use your search program instead of tee
Controlling terminal output on the fly
While running any command in a terminal such as Putty you can use CTRL-S and CTRL-Q to stop and start output to the Putty terminal.
Excluding lines using grep
If you want to exclude lines that contain a specific pattern use grep -v the following would remove all line that contain the string INFO
tail -f logfile | grep -v INFO
Show lines that do not contain the words INFO or DEBUG
tail -f logfile | grep -v -E 'INFO|DEBUG'
Finally, the MOTHER AND FATHER of all tailing tools is xtail.pl
If you have perl on your host xtail.pl is a very nice tool to learn and in a nutshell you can use it to tail multiple files. Very handy.
You can just open it with less command
less logfile_name
when you open the file you can use this guide here
Tip: I suggest, first to use G to go to the end of the file and then to you use Backward Search
I was just wondering what command i need to put into the terminal to read a text file, eliminate all lines that do not contain a certain keyword, and then print those lines onto a new file. for example, the keyword is "system". I want to be able to print all lines that contain system onto a new separate file. Thanks
grep is your friend.
For example, you can do:
grep system <filename> > systemlines.out
man grep and you can get additional useful info as well (ex: line numbers, 1+ lines prior, 1+lines after, negation - ie: all lines that do not contain grep, etc...)
If you are running Windows, you can either install cygwin or you can find a win32 binary for grep as well.
grep '\<system\>'
Will search for lines that contain the word system, and not system as a substring.
below grep command will solve ur problem
grep -i yourword filename1 > filename2
with -i for case insensitiveness
without -i for case sensitiveness
to learn how grep works on ur server ,refer to man page on ur server by the following command
man grep
grep "system" filename > new-filename
You might want to make it a bit cleverer to not include lines with words like "dysystemic", but it's a good place to start.
This question already has answers here:
Colorized grep -- viewing the entire file with highlighted matches
(24 answers)
Closed 7 years ago.
When using grep, it will highlight any text in a line with a match to your regular expression.
What if I want this behaviour, but have grep print out all lines as well? I came up empty after a quick look through the grep man page.
Use ack. Checkout its --passthru option here: ack. It has the added benefit of allowing full perl regular expressions.
$ ack --passthru 'pattern1' file_name
$ command_here | ack --passthru 'pattern1'
You can also do it using grep like this:
$ grep --color -E '^|pattern1|pattern2' file_name
$ command_here | grep --color -E '^|pattern1|pattern2'
This will match all lines and highlight the patterns. The ^ matches every start of line, but won't get printed/highlighted since it's not a character.
(Note that most of the setups will use --color by default. You may not need that flag).
You can make sure that all lines match but there is nothing to highlight on irrelevant matches
egrep --color 'apple|' test.txt
Notes:
egrep may be spelled also grep -E
--color is usually default in most distributions
some variants of grep will "optimize" the empty match, so you might want to use "apple|$" instead (see: https://stackoverflow.com/a/13979036/939457)
EDIT:
This works with OS X Mountain Lion's grep:
grep --color -E 'pattern1|pattern2|$'
This is better than '^|pattern1|pattern2' because the ^ part of the alternation matches at the beginning of the line whereas the $ matches at the end of the line. Some regular expression engines won't highlight pattern1 or pattern2 because ^ already matched and the engine is eager.
Something similar happens for 'pattern1|pattern2|' because the regex engine notices the empty alternation at the end of the pattern string matches the beginning of the subject string.
[1]: http://www.regular-expressions.info/engine.html
FIRST EDIT:
I ended up using perl:
perl -pe 's:pattern:\033[31;1m$&\033[30;0m:g'
This assumes you have an ANSI-compatible terminal.
ORIGINAL ANSWER:
If you're stuck with a strange grep, this might work:
grep -E --color=always -A500 -B500 'pattern1|pattern2' | grep -v '^--'
Adjust the numbers to get all the lines you want.
The second grep just removes extraneous -- lines inserted by the BSD-style grep on Mac OS X Mountain Lion, even when the context of consecutive matches overlap.
I thought GNU grep omitted the -- lines when context overlaps, but it's been awhile so maybe I remember wrong.
You can use my highlight script from https://github.com/kepkin/dev-shell-essentials
It's better than grep cause you can highlight each match with it's own color.
$ command_here | highlight green "input" | highlight red "output"
Since you want matches highlighted, this is probably for human consumption (as opposed to piping to another program for instance), so a nice solution would be to use:
less -p <your-pattern> <your-file>
And if you don't care about case sensitivity:
less -i -p <your-pattern> <your-file>
This also has the advantage of having pages, which is nice when having to go through a long output
You can do it using only grep by:
reading the file line by line
matching a pattern in each line and highlighting pattern by grep
if there is no match, echo the line as is
which gives you the following:
while read line ; do (echo $line | grep PATTERN) || echo $line ; done < inputfile
If you want to print "all" lines, there is a simple working solution:
grep "test" -A 9999999 -B 9999999
A => After
B => Before
If you are doing this because you want more context in your search, you can do this:
cat BIG_FILE.txt | less
Doing a search in less should highlight your search terms.
Or pipe the output to your favorite editor. One example:
cat BIG_FILE.txt | vim -
Then search/highlight/replace.
If you are looking for a pattern in a directory recursively, you can either first save it to file.
ls -1R ./ | list-of-files.txt
And then grep that, or pipe it to the grep search
ls -1R | grep --color -rE '[A-Z]|'
This will look of listing all files, but colour the ones with uppercase letters. If you remove the last | you will only see the matches.
I use this to find images named badly with upper case for example, but normal grep does not show the path for each file just once per directory so this way I can see context.
Maybe this is an XY problem, and what you are really trying to do is to highlight occurrences of words as they appear in your shell. If so, you may be able to use your terminal emulator for this. For instance, in Konsole, start Find (ctrl+shift+F) and type your word. The word will then be highlighted whenever it occurs in new or existing output until you cancel the function.