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Top Forums UNIX for Dummies Questions & Answers Comparing to specific line in file bash script Post 302732083 by ShiGua on Friday 16th of November 2012 02:22:40 PM
Old 11-16-2012
Comparing to specific line in file bash script

Hi,

I have a value stored in x and I need to compare it to the numbers in every other line of a file. The file contains alternating lines of numbers and letters:

aaaa1111
AAAAAAAA
bbbb2222
BBBBBBBB
cccc3333
CCCCCCCC

I need to compare x to the numbers in every other line without the first four characters of that line. So I want to compare x to 1111, then to 2222, then 3333. This is to be the condition in an if statement:

if [ $x = (line 1 without first four characters) ]
or
if [ $x = (line 3 without first four characters) ]

I know I would have to use something along the lines of = $(sed something) or maybe cut, but I don't know how to reference the file by line.

Let me know if I need to be more clear. Thanks for any help!
 

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sdiff(1)						      General Commands Manual							  sdiff(1)

NAME
sdiff - Compares two files and displays the differences in a side-by-side format SYNOPSIS
sdiff [-l | -s] [-w number] [-o output_file] file1 file2 The sdiff command reads file1 and file2, uses diff to compare them, and writes the results to standard output in a side-by-side format. OPTIONS
Displays only the left side when lines are identical. Creates a third file, output_file, by a controlled interactive line-by-line merging of file1 and file2. The following subcommands govern the creation of this file: Adds the left side to output_file. Adds the right side to output_file. Stops displaying identical lines. Begins displaying identical lines. Enters ed with the left side, the right side, both sides, or an empty file, respectively. Each time you exit from ed, sdiff writes the resulting edited file to the end of output_file. If you fail to save the changes before exiting, sdiff writes the initial input to output_file. Exits the interactive session. Suppresses display of identical lines. Sets the width of the output line to number (130 characters by default). DESCRIPTION
The sdiff command displays each line of the two files with a series of spaces between them if the lines are identical, a < (left angle bracket) in the field of spaces if the line only exists in file1, a > (right angle bracket) if the line only exists in file2, and a | (ver- tical bar) for lines that are different. When you specify the -o option, sdiff produces a third file by merging file1 and file2 according to your instructions. Note that the sdiff command invokes the diff -b command to compare two input files. The -b option causes the diff command to ignore trail- ing spaces, tab characters, and consider other strings of spaces as equal. EXAMPLES
To print a comparison of two files, enter: sdiff chap1.bak chap1 This displays a side-by-side listing that compares each line of chap1.bak and chap1. To display only the lines that differ, enter: sdiff -s -w 80 chap1.bak chap1 This displays the differences at the tty. The -w 80 sets page width to 80 columns. The -s option tells sdiff not to display lines that are identical in both files. To selectively combine parts of two files, enter: sdiff -s -w 80 -o chap1.combo chap1.bak chap1 This combines chap1.bak and chap1 into a new file called chap1.combo. For each group of differing lines, sdiff asks you which group to keep or whether you want to edit them using ed. SEE ALSO
Commands: diff(1), ed(1) sdiff(1)
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