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Top Forums UNIX for Dummies Questions & Answers String pattern matching and position Post 302914995 by Don Cragun on Saturday 30th of August 2014 05:34:30 AM
Old 08-30-2014
By definition, grep, sort, and uniq work on text files; and the input your feeding to grep is not a line. (A line ends with a newline character and, including the newline character, contains no more than LINE_MAX bytes. On most systems, LINE_MAX is the minimum allowed by the standards, 2048.)

The standards also require operands to follow options on the command line. So, what you are doing is not portable and will not work at all on many systems.

On Linux systems, where the command you showed might work, it will take a lot longer than processing a normal text file because you require the entire (200Mb) file to be read into the address space of grep at once.

If the command line you showed works on your system, you may be able to get offsets in the file offsets (0-based rather than 1-based) of each match (rather than the number of occurrences of TR, Tr, tR, and tr) by using the command line:
Code:
grep -bio tr oneLineInput.txt

This User Gave Thanks to Don Cragun For This Post:
 

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ZGREP(1)						      General Commands Manual							  ZGREP(1)

NAME
zgrep - search possibly compressed files for a regular expression SYNOPSIS
zgrep [ grep_options ] [ -e ] pattern filename... DESCRIPTION
Zgrep invokes grep on compressed or gzipped files. These grep options will cause zgrep to terminate with an error code: (-[drRzZ]|--di*|--exc*|--inc*|--rec*|--nu*). All other options specified are passed directly to grep. If no file is specified, then the standard input is decompressed if necessary and fed to grep. Otherwise the given files are uncompressed if necessary and fed to grep. If the GREP environment variable is set, zgrep uses it as the grep program to be invoked. EXIT CODE
2 - An option that is not supported was specified. AUTHOR
Charles Levert (charles@comm.polymtl.ca) SEE ALSO
grep(1), gzexe(1), gzip(1), zdiff(1), zforce(1), zmore(1), znew(1) ZGREP(1)
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