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Top Forums Shell Programming and Scripting how to compare file line by line with awk Post 302673153 by alister on Tuesday 17th of July 2012 02:35:14 PM
Old 07-17-2012
Quote:
Originally Posted by kiranps
I have a requirement to compare two files with awk.
file1.txt
a
b
c
d
e

file2.txt
a
b
d
e
Your sample data files have an unequal number of lines but you did not state how to handle that. Is that a typo? If not, should comparison stop when the shorter file's end is reached? Or should the shorter file be treated as if it had enough empty lines to match the excess lines of the longer file? Or perhaps that should just be considered a match?

The following code uses paste, which treats a shorter file as if it had empty lines after end-of-file; it assumes that there are no tab characters in your lines (if there are, a different delimiter is required); and it prints out a line number when there's a difference.

Code:
paste f1 f2 | awk -F'\t' '$1 != $2 {print NR}'

Regards,
Alister

Last edited by alister; 07-17-2012 at 03:45 PM..
 

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PASTE(1)						    BSD General Commands Manual 						  PASTE(1)

NAME
paste -- merge corresponding or subsequent lines of files SYNOPSIS
paste [-s] [-d list] file ... DESCRIPTION
The paste utility concatenates the corresponding lines of the given input files, replacing all but the last file's newline characters with a single tab character, and writes the resulting lines to standard output. If end-of-file is reached on an input file while other input files still contain data, the file is treated as if it were an endless source of empty lines. The options are as follows: -d list Use one or more of the provided characters to replace the newline characters instead of the default tab. The characters in list are used circularly, i.e., when list is exhausted the first character from list is reused. This continues until a line from the last input file (in default operation) or the last line in each file (using the -s option) is displayed, at which time paste begins selecting characters from the beginning of list again. The following special characters can also be used in list: newline character tab character \ backslash character Empty string (not a null character). Any other character preceded by a backslash is equivalent to the character itself. -s Concatenate all of the lines of each separate input file in command line order. The newline character of every line except the last line in each input file is replaced with the tab character, unless otherwise specified by the -d option. If '-' is specified for one or more of the input files, the standard input is used; standard input is read one line at a time, circularly, for each instance of '-'. EXIT STATUS
The paste utility exits 0 on success, and >0 if an error occurs. EXAMPLES
List the files in the current directory in three columns: ls | paste - - - Combine pairs of lines from a file into single lines: paste -s -d ' ' myfile Number the lines in a file, similar to nl(1): sed = myfile | paste -s -d ' ' - - Create a colon-separated list of directories named bin, suitable for use in the PATH environment variable: find / -name bin -type d | paste -s -d : - SEE ALSO
cut(1), lam(1) STANDARDS
The paste utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible. HISTORY
A paste command appeared in Version 32V AT&T UNIX. BSD
June 25, 2004 BSD
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