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On POSIX systems, the file descriptor for standard input is 0 (zero); the POSIX <unistd.h> definition is STDIN_FILENO; the corresponding C <stdio.h> abstraction is provided via the FILE* stdin global variable. Similarly, the global C++ std::cin variable of type <iostream> provides an abstraction via C++ streams.
command > file1 executes command, placing the output in file1, as opposed to displaying it at the terminal, which is the usual destination for standard output. This will clobber any existing data in file1. Using command < file1 executes command, with file1 as the source of input, as opposed to the keyboard, which is the usual source for ...
On DOS, OS/2, and Windows operating systems, the %PATH% variable is specified as a list of one or more directory names separated by semicolon (;) characters. [5]The Windows system directory (typically C:\WINDOWS\system32) is typically the first directory in the path, followed by many (but not all) of the directories for installed software packages.
The %ComSpec% variable contains the full path to the command processor; on the Windows NT family of operating systems, this is cmd.exe, while on Windows 9x, %COMSPEC% is COMMAND.COM. %OS% The %OS% variable contains a symbolic name of the operating system family to distinguish between differing feature sets in batchjobs .
If pushd is not provided with a path argument, in Unix it instead swaps the top two directories on the stack, which can be used to toggle between two directories. The popd command removes (or 'pops', in the stack analogy) the current path entry from the stack and returns to the path at the top of the stack as the new working directory. [4] [5]
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.
File descriptors for a single process, file table and inode table. Note that multiple file descriptors can refer to the same file table entry (e.g., as a result of the dup system call [3]: 104 ) and that multiple file table entries can in turn refer to the same inode (if it has been opened multiple times; the table is still simplified because it represents inodes by file names, even though an ...
While Bash was developed for UNIX and UNIX-like operating systems, such as GNU/Linux, it is also available on Android, macOS, Windows, and numerous other current and historical operating systems. [12] "Although there have been attempts to create specialized shells, the Bourne shell derivatives continue to be the primary shells in use."