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Fairly certain I am missing something obvious!
$ cat test.txt 00 30 * * * /opt/timebomb.sh >> timebomb.log 01 30 * * * /opt/reincarnate.sh >> reincarnation.log $ sed ':timebomb:d' test.txt 00 30 * * * /opt/timebomb.sh >> timebomb.log 01 30 * * * /opt/reincarnate.sh >> reincarnation.log whereas
$ sed '/timebomb/d' test.txt 01 30 * * * /opt/reincarnate.sh >> reincarnation.log Why is it the case? Aren't a different set of delimiters supported for the d command?
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The delimiter of choice is a forward slash (/), which is the most commonly used delimiter. However, sed can use any character as a delimiter. In fact, it will automatically use the character following the s as a delimiter. Note that the expression has to be terminated with the delimiter.
There is no available to delete all contents of the file. How to delete all contents of the file using sed command.
Deleting line using sed To delete a line, we'll use the sed “d” command. Note that you have to declare which line to delete. Otherwise, sed will delete all the lines.
It means that sed will read the next line and start processing it. Your test script doesn't do what you think. It matches the empty lines and applies the delete command to them.
The colon preceeds a label in sed, so your sed program looks like a couple of labels with nothing happening. The parser can see colons as delimiters if preceded by the s command, so that's a special case.
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The delimiters // that you're using are not for the d command, they're for the addressing. I think you're comparing them to the slashes in the s/// command... However although both relate to regular expressions, they are different contexts.
The address (which appears before the command) filters which lines the command is applied to... The options (which appear after the command) are used to control the replacement applied.
If you want to use different delimiters for a regular expression in the address, you need to start the address with a backslash:
$ sed '\:timebomb:d' test.txt 01 30 * * * /opt/reincarnate.sh >> reincarnation.log (To understand the difference between the address and the options, consider the output of the command:
$ sed '/timebomb/s/log/txt/' test.txt The address chooses only the line(s) containing the regular expression timebomb, but the options tell the s command to replace the regular expression log with txt.)
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