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When to use here document or heredoc in Bash?
When writing shell scripts you may be in a situation where you need to pass a multiline block of text or code to an interactive command, such as tee , cat, or sftp . In Bash and other shells like Zsh, a Here document (Heredoc) is a type of redirection that allows you to pass multiple lines of input to a command.
Is there a way to execute multiple commands in heredoc?
Using Heredoc is one of the most convenient and easiest ways to execute multiple commands on a remote system over SSH . When using unquoted delimiter make sure you escape all variables, commands and special characters otherwise they will be interpolated locally:
When to use heredoc in conjunction with Cat?
Heredoc is most often used in combination with the cat command . In the following example, we are passing two lines of text containing an environment variable and a command to cat using a here document. As you can see from the output below, both the variable and the command output are substituted:
What does ” here documents ” mean in Linux?
“Here documents” aren’t documents, and it isn’t really clear what the “here” refers to, either. They are a relatively obscure construct, but they are useful. Of course, this is Linux, so there’s more than one way to skin a cat. Some of the functionality provided by here documents can be reproduced in other ways.
How to overwrite an existing file in heredoc?
To overwrite an existing file (or write to a new file) that you own, substituting variable references inside the heredoc: cat << EOF > /path/to/your/file This line will write to the file. $ {THIS} will also write to the file, with the variable contents substituted. EOF
What can I put in the here document block?
The here-document block can contain strings, variables, commands and any other type of input. The last line ends with the delimiting identifier. White space in front of the delimiter is not allowed. In this section, we will look at some basic examples of how to use heredoc.