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Standard input is a stream from which a program reads its input data. The program requests data transfers by use of the read operation. Not all programs require stream input. For example, the dir and ls programs (which display file names contained in a directory) may take command-line arguments, but perform their operations without any stream ...
Alternatively, if the drain does not need to read any input from stdin to do something useful, it can be given < /dev/null as input. As all components of a pipe are run in parallel, a shell typically forks a subprocess (a subshell) to handle its contents, making it impossible to propagate variable changes to the outside shell environment.
The C programming language provides many standard library functions for file input and output.These functions make up the bulk of the C standard library header <stdio.h>. [1] The functionality descends from a "portable I/O package" written by Mike Lesk at Bell Labs in the early 1970s, [2] and officially became part of the Unix operating system in Version 7.
This runs the ftp client with input user, press return, then pass. In casual use, the initial step of a pipeline is often cat or echo, reading from a file or string. This can often be replaced by input indirection or a here string, and use of cat and piping rather than input redirection is known as useless use of cat. For example, the following ...
In computing, tee is a command in command-line interpreters using standard streams which reads standard input and writes it to both standard output and one or more files, effectively duplicating its input. [1] It is primarily used in conjunction with pipes and filters. The command is named after the T-splitter used in plumbing. [2]
sha1sum — Calculate sha hash for each input file, reading from stdin if none. shred — Securely delete a file by overwriting its contents with random data. sleep — Wait before exiting. sntp — Simple Network Time Protocol client. sort — Sort all lines of text from input files (or stdin) to stdout.
This is because the redirection form opens the file as the stdin file descriptor which command can fully access, while the cat form simply provides the data as a stream of bytes. Another common case where cat is unnecessary is where a command defaults to operating on stdin, but will read from a file, if the filename is given as an argument ...
It allows programs to use the same code to read input from both a terminal and a text file. In the ANSI X3.27-1969 magnetic tape standard, the end of file was indicated by a tape mark , which consisted of a gap of approximately 3.5 inches of tape followed by a single byte containing the character 0x13 (hex) for nine-track tapes and 017 (octal ...