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In computing, redirection is a form of interprocess communication, and is a function common to most command-line interpreters, including the various Unix shells that can redirect standard streams to user-specified locations. The concept of redirection is quite old, dating back to the earliest operating systems (OS).
Makes named pipes (FIFOs) mknod: Makes block or character special files: mktemp: Creates a temporary file or directory mv: Moves files or rename files realpath: Returns the resolved absolute or relative path for a file rm: Removes (deletes) files, directories, device nodes and symbolic links rmdir: Removes empty directories shred
Every pipe is placed in the root directory of the named pipe filesystem (NPFS), mounted under the special path \\.\pipe\ (that is, a pipe named "foo" would have a full path name of \\.\pipe\foo). Anonymous pipes used in pipelining are actually named pipes with a random name. They are very rarely seen by users, but there are notable exceptions.
Anonymous pipe: A unidirectional data channel using standard input and output. Data written to the write-end of the pipe is buffered by the operating system until it is read from the read-end of the pipe. Two-way communication between processes can be achieved by using two pipes in opposite "directions". All POSIX systems, Windows Named pipe
Pipes Command substitution Process substitution Subshells TCP/UDP connections as streams Keystroke stacking; Bourne shell: bytes concurrent Yes No Yes No N/A [nb 19] POSIX shell bytes concurrent Yes No Yes No N/A [nb 19] bash (v4.0) bytes concurrent Yes Yes (if system supports /dev/fd/ n or named pipes) Yes Yes (client only) N/A [nb 19] csh ...
Unix shells use dup2 for input/output redirection. Along with pipe(), it is a tool on which Unix pipes rely. The following example uses pipe() and dup() in order to connect two separate processes (program1 and program2) using Unix pipes:
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Process substitution can also be used to capture output that would normally go to a file, and redirect it to the input of a process. The Bash syntax for writing to a process is >(command) . Here is an example using the tee , wc and gzip commands that counts the lines in a file with wc -l and compresses it with gzip in one pass: