Printing Grep Results to File and Terminal

Printing grep results to file and terminal

The program you are looking for is "tee":

grep -n "$SEARCH_TERM" "$i" | tee -a /file.txt

How do I fetch lines before/after the grep result in bash?

You can use the -B and -A to print lines before and after the match.

grep -i -B 10 'error' data

Will print the 10 lines before the match, including the matching line itself.

How do I make grep output to a file?

This works here:

grep -i "other something" *.txt >> tables.txt

How do I get the dates of files in my output from a grep search?

The problem is that grep is outputting the line that match your string, not the file name, so that in your second example your trying to call stat on a string, not on a file!

You should add a -l parameter to your grep command in order to not output the matching line but the file that contains it. Try this:

grep -lrnw '/my_path/' -e 'search_string' | stat -c %n':'%z > list.txt

[EDIT] Anyway this would not work because the stat command does not accept input from a pipe. The solution is then

stat -c %n':'%z $(grep -lrnw '/my_path/' -e 'search_string') > list.txt

grepping using the result of previous grep

You're almost there. But while xargs can sometimes be used to do what you want (depending on how the next command takes its arguments), you aren't actually using it to grep for the ID you just extracted. What you need to do is take the output of the first grep (containing the ID code) and use that in the next grep's expression. Something like:

grep "^ID `grep 'xyz occured' file.log | awk '{print $2}'` status code" file.log

Obviously another option would be to write a script to do this in one pass, a-la Ed's suggestion.

How to pipe output from grep to cp?

grep -l -r "TWL" --exclude=*.csv* | xargs cp -t ~/data/lidar/tmp-ajp2/

Explanation:

• grep -l option to output file names only
• xargs to convert file list from the standard input to command line arguments
• cp -t option to specify target directory (and avoid using placeholders)

Pipe output with tee & grep into file but seeing full output

Then maybe not grep, you can use awk instead:

cat file | awk '/aaa/{print >>"output.txt";}1'

How can I format my grep output to show line numbers at the end of the line, and also the hit count?

-n returns line number.

-i is for ignore-case. Only to be used if case matching is not necessary

$ grep -in null myfile.txt

2:example two null,
4:example four null,

Combine with awk to print out the line number after the match:

$ grep -in null myfile.txt | awk -F: '{print $2" - Line number : "$1}'

example two null, - Line number : 2
example four null, - Line number : 4

Use command substitution to print out the total null count:

$ echo "Total null count :" $(grep -ic null myfile.txt)

Total null count : 2

How to grep and execute a command (for every match)

grep file foo | while read line ; do echo "$line" | date %s.%N ; done

More readably in a script:

grep file foo | while read line
do
    echo "$line" | date %s.%N
done

For each line of input, read will put the value into the variable $line, and the while statement will execute the loop body between do and done. Since the value is now in a variable and not stdin, I've used echo to push it back into stdin, but you could just do date %s.%N "$line", assuming date works that way.

Avoid using for line in `grep file foo` which is similar, because for always breaks on spaces and this becomes a nightmare for reading lists of files:

 find . -iname "*blah*.dat" | while read filename; do ....

would fail with for.

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