UNIX-LINUX OPERATING SYSTEM 1201376 BECOMING A DIVIDERLINUX POWER SLIDEUSER SectionPipes and title filters Olarik Surinta, PhD. Lecturer Pipe (|) ● The symbol ‘|’ denotes a pipe. ● If you want to use two or more commands at the same time and run them consecutively, you can use pipes. ● A filter in a pipe is an output of one command which serves as input to the next. 3 Pipe ● Commands that are create to be used with a pipe are often called filters. ● These filters are very small programs that do one specific thing very efficiently. ● The combination of simple commands and filters in a long pipe allows you to design elegant solutions. 4 grep ● The grep filter is famous among Unix users. ● The most common use of grep is to filter lines of text containing (or not containing) a certain string. 5 grep $ cat tennis.txt Amelie Mauresmo, Fra Kim Clijsters, BEL Justine Henin, Bel Serena Williams, Usa Venus Williams, USA $ cat tennis.txt | grep Williams Serena Williams, Usa Venus Williams, USA 6 grep ● You can write command without the cat. $ grep Williams tennis.txt Serena Williams, usa Venus Williams, USA 7 grep ● One of the most useful options of grep is gerp -i which filters in a case insensitive way. $ grep Bel tennis.txt Justine Henin, Bel $ grep -i Bel tennis.txt Kim Clijsters, Bel Justine Henin, Bel 8 grep ● Another very useful option is grep -v which outputs lines not matching the string. $ grep -v Fra tennis.txt Kim Clijsters, BEL Justine Henin, Bel Serena Williams, usa Venus Williams, USA 9 grep ● And of course, both options can be combined to filter all lines not containing a case insensitive string. $ grep -vi usa tennis.txt Amelie Mauresmo, Fra Kim Clijsters, BEL Justine Henin, Bel 10 cut ● The cut filter can select columns from files, depending on a delimiter. ● When using a space as the delimiter for cut, you have to quote the space. $ cut -d " " -f 1 tennis.txt Amelie Kim Justine Serena Venus 11 tr ● You can translate characters with tr. $ cat tennis.txt | tr 'a-z' 'A-Z' AMELIE MAURESMO, FRA KIM CLIJSTERS, BEL JUSTINE HENIN, BEL SERENA WILLIAMS, USA VENUS WILLIAMS, USA 12 sort ● The sort filter will default to an alphabetical sort. $ cat music.txt Queen Brel Led Zeppelin Abba 13 sort $ sort music.txt Abba Brel Led Zeppelin Queen 14 sort ● -r option is reverse the result of comparisons $ sort -r music.txt Queen Led Zeppelin Brel Abba 15 Pipe examples ● How many users are logged on to this system? $ who mrolarik tty7 2017-09-02 12:01 (:0) mrolarik pts/13 2017-09-04 16:04 (:0.0) $ who | wc -l 2 16 Pipe examples ● Cat | grep | sort $ cat tennis.txt grep -i bel | sort Justine Henin, Bel Kim Clijsters, BEL $ cat tennis.txt | grep -i bel | sort | tr 'a-z' 'A-Z' JUSTINE HENIN, BEL KIM CLIJSTERS, BEL 17 Pipe examples $ find /etc | grep -i java.*jdk /etc/java-8-openjdk /etc/java-8-openjdk/management /etc/java-8-openjdk/management/snmp.acl grep -i java.*jdk End with “jdk” Start with “java” .* = any words between “java” and “jdk” 18 File globbing ● * asterisk ● ? question mark ● [] square brackets ● A-z and 0-9 ranges 19 * asterisk ● The asterisk * in interpreted by the shell as a sign to generate filenames, matching the asterisk to any combination of characters. ● When no path is given, the shell will use filenames in the current directory. 20 * asterisk 21 ? question mark ● Similar to the asterisk, the question mark ? Is interpreted by the shell as a sign to generate filenames, matching the question mark with exactly one character. 22 ? question mark 23 [] square brackets ● The square bracket is interpreted by the shell as a sign to generate filenames, matching any of the characters between [ and the first subsequent ]. ● The order in this list between the brackets is not important. ● Each pair of brackets is replaced by exactly one character. 24 [] square brackets 25 a-z and 0-9 ranges ● The bash shell will also understand ranges of characters between brackets. 26 reference ● Linux Fundamentals – Paul Cobbaut ● Website – https://www.guru99.com/linux-pipe-grep. html – – 27.