Visit Our UNIX and Linux User Community


Sed: would like to return an error for empty string


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Sed: would like to return an error for empty string
# 1  
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.
# 2  
Old 04-13-2020
Try testing for "start-of-line nothing end-of-line":

Code:
echo "" | sed -n -r '/[0-9]{3}/{q100}; /^$/{q200}'; echo $?
200

And, wouldn't it make sense to have different codes for different errors?
This User Gave Thanks to RudiC For This Post:
# 3  
Old 04-13-2020
Quote:
Originally Posted by RudiC
Try testing for "start-of-line nothing end-of-line":

Code:
echo "" | sed -n -r '/[0-9]{3}/{q100}; /^$/{q200}'; echo $?
200

And, wouldn't it make sense to have different codes for different errors?
Indeed. I've just added them. Smilie



Such a simple solution. Thanks so much.

Previous Thread | Next Thread
Test Your Knowledge in Computers #438
Difficulty: Medium
TypeScript is a free and open-source subset of JavaScript developed by Microsoft.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Cant check empty string

Hello So i have that script collection, in which i have a single script to create a configuration file. In there, i have multiple occourences of something like this: prj_title=$(tui-read "What is the TITLE? ($prj_name):") ] && prj_title="${prj_name/_/ }" They all work as expected, if... (5 Replies)
Discussion started by: sea
5 Replies

2. Shell Programming and Scripting

Unzipping the empty file sends a non Zero return code

Hi, I have a shell script where I am trying to unzip bunch of files zip files one by one. But out of many zip files, if any one zip file is empty, the unzip command sends a non-zero return code and fails the script. I am trying to see if I can get a success error code even if the script... (2 Replies)
Discussion started by: Saanvi1
2 Replies

3. Shell Programming and Scripting

Check if the string is empty

I am reading from a file and executing the jobs with/without parameters as the job requires. File job1 R job2 job3 Y 123 if then <job>.ksh else <job>.ksh $params fi This works fine if the line read from the file has parameters it executes like job1.ksh R But for... (2 Replies)
Discussion started by: nw2unx123
2 Replies

4. Programming

Checking not empty string

I have a string s Are the following equivalent? if ( ! s.empty() ) { } if ( s ) { } (1 Reply)
Discussion started by: kristinu
1 Replies

5. Shell Programming and Scripting

sed or awk command to replace a string pattern with another string based on position of this string

here is what i want to achieve... consider a file contains below contents. the file size is large about 60mb cat dump.sql INSERT INTO `table1` (`id`, `action`, `date`, `descrip`, `lastModified`) VALUES (1,'Change','2011-05-05 00:00:00','Account Updated','2012-02-10... (10 Replies)
Discussion started by: vivek d r
10 Replies

6. Shell Programming and Scripting

error while replacing a string by new line character in sed

hi, when i am doing the following things getting error Can anyone please suggest i have a file where there is a line like the following branch=dev sdf dev jin kilii fin kale boyle dev james dev i want to search the existance of dev in the above line. cat "$file" | sed -n... (8 Replies)
Discussion started by: millan
8 Replies

7. Shell Programming and Scripting

Need Help to deal with empty string

Hi one to All i have written the code for searching the string in the file for specified path. its working fine, but my req:if the string is not available in the file , it should display the Message saying that , string is not available in the file. code is: echo "give the path where... (12 Replies)
Discussion started by: saic
12 Replies

8. UNIX for Dummies Questions & Answers

to check if file is empty or not and return a non zero value

Hi All, I am new to unix worldd . I need to check a file1 if its empty or not. If its empty then return a non zero value say 99 could you pls let me know the perl script for this. (2 Replies)
Discussion started by: mavesum
2 Replies

9. Shell Programming and Scripting

Check for empty string

Hello All, I have written shell script whcih at the max 3 parameters. When only one commandline argument and other two command line arguments are passed as empty string like eg : archive ' ' ' ' Then i need to check whether the commandline... (12 Replies)
Discussion started by: rahman_riyaz
12 Replies

10. Shell Programming and Scripting

How to check for null or empty string

Hi, I need to check for value not equal (<>) to 21 and not equal empty or null values. Please modify this script if then echo "$VALUE,$BSC_NAME,$BSC_ID" > $OUT_FILE/power_up.out end if TQ (5 Replies)
Discussion started by: doer
5 Replies

Featured Tech Videos