How to work with substrings on Linux

$ echo "Concentrate on Peace on Earth" | reduce -d' ' -f3,5
Peace Earth
$ echo "one two three 4 5 6" | reduce -d' ' -f1-3,6
one two three 6

To make use of an alternate delimiter (on this case, a colon), use a command like this:

$ reduce -d':' -f1-3,5,6 /and so forth/passwd | tail -n 5
justme:x:1004:JustMe:/dwelling/justme
lola:x:1006::/dwelling/lola
dumdum:x:1007::/dwelling/dumdum

With awk, you need to use a couple of delimiter. Within the following instance, two delimiters are specified, so the awk command accepts both a colon or a clean to separate fields. The primary two strains show the file, and the final two strains present the command and end result.

$ cat file
Monday:1 Tuesday:2 Wednesday:3 Thursday:4 Friday:5
$ awk -F'[: ]' 'OFS=" ";print $1,$3,$4' file
Monday Tuesday 2

Choosing substrings

To pick out an arbitrary sequence or characters from a string, you need to use an awk command just like the one under during which the $0 represents the whole phrase, 10 represents the primary character place to be grabbed and 5 is the size of the string to be displayed.

$ echo "Concentrate on Peace" | awk 'print substr($0,10,5)'
Peace

To do the identical type of factor with the reduce command, you’d use a command like this during which the 13^th by 22^nd characters are extracted from the phrase and displayed.

$ echo "Linux is a formidable OS" | reduce -c 13-22
spectacular

On this subsequent command, the reduce command shows the 7^th-12^th characters from the strains in a file. The head command merely limits the show to the primary 4 strains of output.

$ reduce -c 7-12 sayings | head -4
with 3
and ov
nd be
and be

Utilizing grep

You should utilize the grep command to pick a number of phrases from a file. On this instance, solely the chosen phrases are displayed, not the whole strains. It’s because the -o (show solely the matched objects) choice is getting used.