How to use sed to replace only the first occurrence in a file?

Question

I would like to update a large number of C++ source files with an extra include directive before any existing #includes. For this sort of task, I normally use a small bash s

Answer 1

The following command removes the first occurrence of a string, within a file. It removes the empty line too. It is presented on an xml file, but it would work with any file.

Useful if you work with xml files and you want to remove a tag. In this example it removes the first occurrence of the "isTag" tag.

Command:

sed -e 0,/'false<\/isTag>'/{s/'false<\/isTag>'//}  -e 's/ *$//' -e  '/^$/d'  source.txt > output.txt

Source file (source.txt)

    
        true
        false
        
            esa_jee6
            false
        
        
            false
        
    

Result file (output.txt)

    
        true
        
            esa_jee6
            false
        
        
            false
        
    

ps: it didn't work for me on Solaris SunOS 5.10 (quite old), but it works on Linux 2.6, sed version 4.1.5