Stdin/Stdout/Stderr

Definitions

1. The three standard I/O streams in Unix: stdin (fd 0, input), stdout (fd 1, normal output), and stderr (fd 2, error output). The Unix philosophy of composing small programs relies on piping stdout of one program into stdin of another. Separating stdout and stderr allows redirecting errors independently.

   In plain English: The three default channels for data flowing in and out of a command-line program: input, output, and errors.

   Example: "Pipe stdout to jq for parsing but let stderr go to the terminal so you can see errors: curl url 2>/dev/tty | jq ."

Related Terms

• Async
• Buffer
• Redirection
• String
• Standard Output
• Stderr
• Stdin
• Stdout
• TTY