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Full Discussion: Need help deciphering this
Top Forums UNIX for Dummies Questions & Answers Need help deciphering this Post 302416821 by Straitsfan on Tuesday 27th of April 2010 09:58:05 PM
Old 04-27-2010
Need help deciphering this

I'm reading about command substitutions and came across this little function in my book:

function lsd
{
date=$1
ls -l |grep -i "^.\{42\}$date"|cut -c55-
}

it's a little example which is supposed to select files by modification date, given as an argument to the function.

I can't figure out what the ^, ., and \{42\} means. The book says that the function tells UNIX to match any line that contains 41 characters followed by the function argument, with the date starting in column 42, then only printing the filenames, which start in column 55, but like I said I don't know what these symbols mean (or how they 'translate'). The only thing I've found about the ^ so far is that it's a 'word designator' but I'm not sure if that applies here.

I'm also not sure how to translate the .\{42\} either.

By the way, how do I find out what the column layout for the ls -l command is? (if I've phrased that correctly), that is, what column each part of the listing begins at?
 

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grep-changelog(1)					      General Commands Manual						 grep-changelog(1)

NAME
grep-changelog - print ChangeLog entries matching criteria SYNOPSIS
grep-changelog [options] [CHANGELOG...] DESCRIPTION
grep-changelog searches the named CHANGELOGs (by default files matching the regular expressions ChangeLog and ChangeLog.[0-9]+) for entries matching the specified criteria. At least one option or file must be specified. This program is distributed with GNU Emacs. OPTIONS
The program accepts unambiguous abbreviations for option names. --author=AUTHOR Print entries whose author matches regular expression AUTHOR. --text=TEXT Print entries whose text matches regular expression TEXT. --exclude=TEXT Exclude entries matching regular expression TEXT. --from-date=YYYY-MM-DD Only consider entries made on or after the given date. ChangeLog date entries not in the "YYYY-MM-DD" format are never matched. --to-date=YYYY-MM-DD Only consider entries made on or before the given date. --rcs-log Print output in a format suitable for RCS log entries. This format removes author lines, leading spaces, and file names. --with-date In RCS log format, print short dates. --reverse Show matches in reverse order. --version Display version information. --help Display basic usage information. COPYING
Copyright (C) 2008, 2009 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this document provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this document under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this document into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation. grep-changelog(1)
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