ACS Unix (Winter Term, ) Page 51

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1 ACS Unix (Winter Term, ) Page 51 Unix sets up the output file before starting the cat program. Thus, the file name will be cleared out before cat reads and combines its input. By the time cat looks in name, it is already empty. If you want to add address and phone to name, you can cat address phone >> name Extract Selected Columns of Each Line: cut The cut command extracts columns of data. One of the syntaxes of the cut command is: cut c list [file ] where list is a list of columns to be extracted. cat students Ambercrombie, 01/01/ Barton, 02/02/ Canby, Charles 03/03/ Danfield, Deann 04/04/ pearl % cut -c students Ambercrombie, Barton, Canby, Charles Danfield, Deann... pearl % pearl % cut -c 14-30,42-49 students Ambercrombie, Barton, Canby, Charles Danfield, Deann pearl %

2 ACS Unix (Winter Term, ) Page 52 Another important syntax of the cut command is: cut f list [-d delim ] [-s] [file ] The list following the f option is a list of fields assumed to be separated by a delimiter character. cat students.backup :Ambercrombie, :01/01/72: :Barton, :02/02/73: :Canby, Charles:03/03/74: :Danfield, Deann:04/04/75: cut -f 1 d ':' students.backup cut -f 2,4 d ':' students.backup Ambercrombie, : Barton, : Canby, Charles: Danfield, Deann:

3 ACS Unix (Winter Term, ) Page 53 Combining Columns of Data: paste The paste command combines columns of data and has a great deal of flexibility. The syntax of the paste command is: paste [-d char] file (d: delimiter) where char is a character to be used as a separator. cat id cat name Ambercrombie, Barton, Canby, Charles Danfield, Deann cat birthday 01/01/92 02/02/93 03/03/94 04/04/95 cat phone paste -d'$' id name birthday phone > info cat info $Ambercrombie, $01/01/92$ $Barton, $02/02/93$ $Canby, Charles$03/03/94$ $Danfield, Deann $04/04/95$

4 ACS Unix (Winter Term, ) Page 54 Check Data for Spelling Errors: spell The spell command will read data and generate a list of all the words that look as if they are misspelled. The spell command is actually one of a family of programs that uses a master file of stored words to provide a spell-checking service. This file is /usr/share/dict/words (could be a link). The syntax of the spell command is: spell file cat test_file The background color of my cheque is light bluue. spell test_file cheque bluue Extracting Lines Beginning with a Specified Pattern: look The look command will search data that is in alphabetical order and will find all the lines that begin with a specified pattern. The syntax of the look command is: look [-df] string [file ] where string is the pattern to search for. -d Tell look to consider only upper and lowercase letters, numbers, tabs, and spaces. -f Tell look to treat uppercase the same as lowercase. look cannot read from the standard input. Thus, it is not really a filter and cannot be used within a pipeline.

5 ACS Unix (Winter Term, ) Page 55 Example: look 3 info $Danfield, Deann $04/04/95$ If you use look without specifying a source of input, look will examine the file /usr/share/dict/words, using both the d and f options. look winn Winnebago Winnebago's Winnie Winnipeg Winnipeg's winner winner's winners winning winning's winnings winnow winnowed winnowing winnows look look look look's lookalike lookalike's lookalikes looked looking lookout lookout's lookouts looks

6 ACS Unix (Winter Term, ) Page 56 Counting Lines, Words, and Characters: wc The wc (word count) command counts lines, words, and characters. (wc considers a word to be an unbroken sequence of characters.) The syntax of the wc command is: Example: wc [-lwc] [file ] -l counts lines -w counts words -c counts characters cat names wc names names In this case, the file names has 5 lines, 5 words, and 28 characters. You can specify more than one file at a time. For example, wc file1 file2 file3 might output file file file total

7 ACS Unix (Winter Term, ) Page 57 Sorting Data: sort The syntax for using sort to sort data is: sort [-dfru] [-o outfile] [infile ] -d considers only letters, numerals, and spaces. -f treats uppercase letters as lowercase. -r sorts the data in reverse order. -u looks for identical lines and suppress all but one. outfile is the name of a file to hold the output, and infile is the name of a file that contains input. cat names sort names sort -u names sort -ru names

8 ACS Unix (Winter Term, ) Page 58 The o option will allow you to save the output in the same file. sort o names names will sort the contents of names and save the sorted result in names. sort o names names oldnames extranames will sort the data from names, oldnames, and extranames, and save the output in the file names. The ASCII Code By default, data is stored in ascending order according to a specification called the ASCII code. The ASCII code is a description of the entire set of 128 different characters. The order of characters in the ASCII code is as follows: control characters (including the tab) the space character (symbols)! " # $ % & ' ( ) * +, -. / (the numerals) (more symbols) : ; < = (uppercase letters) A B C Z (more symbols) [ \ ] ^ _ ` (lowercase letters) a b c z (more symbols) { } ~ the del (null) character

CS160A EXERCISES-FILTERS2 Boyd

CS160A EXERCISES-FILTERS2 Boyd Exercises-Filters2 In this exercise we will practice with the Unix filters cut, and tr. We will also practice using paste, even though, strictly speaking, it is not a filter. In addition, we will expand