How do you grep only few lines?

The syntax is:

1. Use single quotes in the pattern: grep ‘pattern*’ file1 file2.
2. Next use extended regular expressions: egrep ‘pattern1|pattern2’ *. py.
3. Finally, try on older Unix shells/oses: grep -e pattern1 -e pattern2 *. pl.
4. Another option to grep two strings: grep ‘word1\|word2’ input.

How can I get unique grep results?

Solution:

1. Using grep and head command. Pipe the output of grep command to head command to get the first line.
2. Using m option of grep command. The m option can be used to display the number of matching lines.
3. Using the sed command. We can also use the sed command to print unique occurrence of a pattern.
4. Using awk command.

What is grep invert match?

Today I learned about the -v flag for grep . The -v , or –invert-match , flag, returns all lines that do not match your regular expression. Let’s say you have a long list of items, and you want to narrow it down to the ones that are not orange.

How do you grep recursively?

To recursively search for a pattern, invoke grep with the -r option (or –recursive ). When this option is used grep will search through all files in the specified directory, skipping the symlinks that are encountered recursively.

How do you negate grep?

To invert the Grep output , use the -v flag. The -v option instructs grep to print all lines that do not contain or match the expression. The –v option tells grep to invert its output, meaning that instead of printing matching lines, do the opposite and print all of the lines that don’t match the expression.

What is grep R?

The grep R function returns the indices of vector elements that contain the character “a” (i.e. the second and the fourth element). The grepl function, in contrast, returns a logical vector indicating whether a match was found (i.e. TRUE) or not (i.e. FALSE).