Questão de Linux Administration #019e3987

In Bash, stream redirection operators are used to control where input and output of commands are directed. The valid operators among the options are <, <<<, and >.

How it Works

• <: Redirects the contents of a file as standard input to a command. For example, command < file.txt makes the command read from file.txt instead of the keyboard.
• <<<: Known as a "here string," it redirects a string as standard input to a command. For example, command <<< "string" passes the string as input.
• >: Redirects standard output of a command to a file, overwriting the file if it exists. For example, command > file.txt writes the command's output to file.txt.

Why the Correct Values are Right

• <: This is a standard input redirection operator defined in POSIX shells. It is widely used to feed file content into commands.
• <<<: This is a Bash-specific operator (also available in some other shells like Zsh) that provides a convenient way to pass a string as input without using a temporary file or a here-document.
• >: This is a standard output redirection operator. It is fundamental for saving command output to files.

Why the Incorrect Values are Wrong

• >>>: This is not a valid redirection operator in Bash. The double greater-than sign >> is valid for appending output to a file, but triple >>> has no meaning and will cause a syntax error.
• %>: This is not a valid redirection operator in Bash. The percent sign is not used in redirection syntax; it is used in job control (e.g., %1 to refer to job number 1) or in pattern matching. Using %> will result in an error.