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Top Forums Shell Programming and Scripting Sed: would like to return an error for empty string Post 303045785 by bedtime on Monday 13th of April 2020 09:00:26 AM
Old 04-13-2020
Sed: would like to return an error for empty string

There are actually two things that I want to do:

1. Detect if there is a 3 digit number and if so return an error (working)
2. Detect if there is an empty string and return an error if so (not working)

I would like to do 1 & 2 using the sed command only once; I'm trying to do things correctly and efficiently.

I have so far:
Code:
echo "" | sed -n -r '/[0-9]{3}/{q100}; //{q100}'; echo $?

(For newbies: -n quiets text output, -r allows for GNU program to do true regex, {q100} returns error '100', '$?' is the last returned result)



The result is 0, which is not what I want as the string is empty. My attempt is the portion '//{q100}', but I can see that it is difficult to test against nothing-quite perplexing actually.
 

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textutil::split(n)				    Text and string utilities, macro processing 				textutil::split(n)

__________________________________________________________________________________________________________________________________________________

NAME
textutil::split - Procedures to split texts SYNOPSIS
package require Tcl 8.2 package require textutil::split ?0.7? ::textutil::split::splitn string ?len? ::textutil::split::splitx string ?regexp? _________________________________________________________________ DESCRIPTION
The package textutil::split provides commands that split strings by size and arbitrary regular expressions. The complete set of procedures is described below. ::textutil::split::splitn string ?len? This command splits the given string into chunks of len characters and returns a list containing these chunks. The argument len defaults to 1 if none is specified. A negative length is not allowed and will cause the command to throw an error. Providing an empty string as input is allowed, the command will then return an empty list. If the length of the string is not an entire multiple of the chunk length, then the last chunk in the generated list will be shorter than len. ::textutil::split::splitx string ?regexp? This command splits the string and return a list. The string is split according to the regular expression regexp instead of a simple list of chars. Note that if you parentheses are added into the regexp, the parentheses part of separator will be added into the result list as additional element. If the string is empty the result is the empty list, like for split. If regexp is empty the string is split at every character, like split does. The regular expression regexp defaults to "[\t \r\n]+". BUGS, IDEAS, FEEDBACK This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category textutil of the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas for enhancements you may have for either package and/or documentation. SEE ALSO
regexp(n), split(n), string(n) KEYWORDS
regular expression, split, string CATEGORY
Text processing textutil 0.7 textutil::split(n)
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