Search results
Results from the WOW.Com Content Network
If the merged output is to be piped into another program, the file merge sequence 2>&1 must precede the pipe symbol, thus, find /-name.profile 2 > & 1 | less A simplified but non-POSIX conforming form of the command, command > file 2 > & 1 is (not available in Bourne Shell prior to version 4, final release, or in the standard shell Debian ...
An important aspect of this, setting Unix pipes apart from other pipe implementations, is the concept of buffering: for example a sending program may produce 5000 bytes per second, and a receiving program may only be able to accept 100 bytes per second, but no data is lost. Instead, the output of the sending program is held in the buffer.
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.
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:
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:
The name "pipeline" comes from a rough analogy with physical plumbing in that a pipeline usually [2] allows information to flow in only one direction, like water often flows in a pipe. Pipes and filters can be viewed as a form of functional programming, using byte streams as data objects.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
The name tee comes from this scheme - it looks like the capital letter T. The tee command is normally used to split the output of a program so that it can be both displayed and saved in a file. The command can be used to capture intermediate output before the data is altered by another command or program.