Can you grep the output of a command?

Can you grep the output of a command?

Using Grep to Filter the Output of a Command A command’s output can be filtered with grep through piping, and only the lines matching a given pattern will be printed on the terminal. You can also chain multiple pipes in on command.

How extract only number from string in Unix?

10 Answers

1. Replaces all line breaks with spaces: tr ‘\n’ ‘ ‘
2. Replaces all non numbers with spaces: sed -e ‘s/[^0-9]/ /g’
3. Remove leading white space: -e ‘s/^ *//g’
4. Remove trailing white space: -e ‘s/ *$//g’
5. Squeeze spaces in sequence to 1 space: tr -s ‘ ‘
6. Replace remaining space separators with line break: sed ‘s/ /\n/g’

How do you count after grep?

Using grep -c alone will count the number of lines that contain the matching word instead of the number of total matches. The -o option is what tells grep to output each match in a unique line and then wc -l tells wc to count the number of lines. This is how the total number of matching words is deduced.

How do I redirect the output of a grep command?

grep -n “test” * | grep -v “mytest” > output-file will match all the lines that have the string “test” except the lines that match the string “mytest” (that’s the switch -v ) – and will redirect the result to an output file.

What is Bash_rematch?

It’s called BASH_REMATCH. Think of REMatch as Regular Expression Match, not the English word Rematch. If a Bash regular expression matches a string, the return code is zero and the matched portion is placed inside the BASH_REMATCH array.

How do you count the number of words in a Unix file?

The wc (word count) command in Unix/Linux operating systems is used to find out number of newline count, word count, byte and characters count in a files specified by the file arguments. The syntax of wc command as shown below.

How do I count the number of words in a Unix file?

How to find the total count of a word / string in a file?

1. Using the grep command: $ grep -o ‘Unix’ file | wc -l 4.
2. tr command: $ tr -s ” ” “\n” < file | grep -c Unix 4.
3. awk solution: $ awk ‘/Unix/{x++}END{print x}’ RS=” ” file 4.
4. Perl solution: $ perl -ne ‘$x+=s/Unix//g;END{print “$x\n”}’ file 4.
5. Another Perl solution:

How do you store grep output in a variable?

How to assign a grep command value to a variable in Linux/Unix

1. VAR=`command-name` VAR=”`grep word /path/to/file`” ## or ## VAR=$(command-name) VAR=”$(grep word /path/to/file)”
2. echo “Today is $(date)” ## or ## echo “Today is `date`”
3. todays=$(date)
4. echo “$todays”
5. myuser=”$(grep ‘^vivek’ /etc/passwd)” echo “$myuser”

How to limit the number of lines in the grep output?

Limit the number of lines in the grep output by adding the -m option and a number to the command. grep -m2 Phoenix sample In this case, the terminal prints the first two matches it finds in the sample file.

How do I grep all files in a directory in Linux?

To include all subdirectories in a search, add the -r operator to the grep command. grep -r phoenix * This command prints the matches for all files in the current directory, subdirectories, and the exact path with the filename. In the example below, we also added the -w operator to show whole words, but the output form is the same.

How to grep extended regular expressions in Linux?

You can use grep -E to access the extended regular expression syntax ( Same as egrep) I have created a testfile with below contents: will be output. Here “-o” is used to only output the matching segment of the line, rather than the full contents of the line.

How to grep only the matched text instead of the whole?

The o option makes grep print only the matched text, instead of the whole line. Another way is to use a text editor directly. With Vim, one of the various ways of accomplishing this would be to delete lines without name= and then extract the content from the resulting lines: