CODEWITHSUNDEEP
bashio-redirection
Sudip Bhattarai
Sudip Bhattarai

Reputation: 1144

Pre-fill stdin for a process in bash

I want a process to keep reading inputs from stdin after sending a string to it initially. How can i do it in bash?

here is a incorrect solution to explain what i am trying to do.

echo "$HEADER" | cat - < /dev/stdin

Here cat command must receive the content of $HEADER first then behave like how cat - should behave.

Upvotes: 0

Views: 514

Answers (1)

that other guy
that other guy

Reputation: 123410

You can pipe multiple commands in sequence, where the the first writes a header and the second is just cat to relay input from stdin to stdout:

{ echo "$HEADER"; cat; } | yourcommand

The problem with your approach is that you can only ever have one stdin, while you try to use two. echo "foo" | cat /dev/stdin /dev/tty could have been an option, but this unnecessarily relies on having a terminal.

Upvotes: 5

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