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The command can be used to capture intermediate output before the data is altered by another command or program. The tee command reads standard input, then writes its content to standard output. It simultaneously copies the data into the specified file(s) or variables. The syntax differs depending on the command's implementation.
In the case of an interactive shell, that is usually the text terminal which initiated the program. The file descriptor for standard output is 1 (one); the POSIX <unistd.h> definition is STDOUT_FILENO; the corresponding C <stdio.h> variable is FILE* stdout; similarly, the C++ <iostream> variable is std::cout.
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.
A command-line interface (CLI) is a means of interacting with a computer program by inputting lines of text called command lines. Command-line interfaces emerged in the mid-1960s, on computer terminals , as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards .
In these languages, including the line __DATA__ (Perl) or __END__ (Ruby, old Perl) marks the end of the code segment and the start of the data segment. Only the contents prior to this line are executed, and the contents of the source file after this line are available as a file object: PACKAGE::DATA in Perl (e.g., main::DATA) and DATA in Ruby ...
In shells derived from csh (the C shell), the syntax instead appends the & (ampersand) character to the redirect characters, thus achieving a similar result. The reason for this is to distinguish between a file named '1' and stdout, i.e. cat file 2 >1 vs cat file 2 > & 1.
A pointer is a data type that contains the address of a storage location of a variable of a particular type. They are declared with the asterisk (*) type declarator following the basic storage type and preceding the variable name. Whitespace before or after the asterisk is optional.
In 1964, the expression READ-EVAL-PRINT cycle is used by L. Peter Deutsch and Edmund Berkeley for an implementation of Lisp on the PDP-1. [3] Just one month later, Project Mac published a report by Joseph Weizenbaum (the creator of ELIZA, the world's first chatbot) describing a REPL-based language, called OPL-1, implemented in his Fortran-SLIP language on the Compatible Time Sharing System (CTSS).