Plan 9 from Bell Labs is a distributed operating system which originated from the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s and built on UNIX concepts first developed there in the late 1960s. Since 2000, Plan 9 has been free and open-source. The final official release was in early 2015.
In Unix and Unix-like operating systems, chmod is the command and system call used to change the access permissions and the special mode flags of file system objects. Collectively these were originally called its modes, and the name chmod was chosen as an abbreviation of change mode.
uniq is a utility command on Unix, Plan 9, Inferno, and Unix-like operating systems which, when fed a text file or standard input, outputs the text with adjacent identical lines collapsed to one, unique line of text.
In computing, ls is a command to list computer files and directories in Unix and Unix-like operating systems. It is specified by POSIX and the Single UNIX Specification.
The cd command, also known as chdir, is a command-line shell command used to change the current working directory in various operating systems. It can be used in shell scripts and batch files.
In computing, a symbolic link is a file whose purpose is to point to a file or directory by specifying a path thereto.
Unix security refers to the means of securing a Unix or Unix-like operating system. A secure environment is achieved not only by the design concepts of these operating systems, but also through vigilant user and administrative practices.
In computing, touch is a command used to update the access date and/or modification date of a computer file or directory. It is included in Unix and Unix-like operating systems, TSC's FLEX, Digital Research/Novell DR DOS, the AROS shell, the Microware OS-9 shell, and ReactOS. The command is also available for FreeDOS and Microsoft Windows.
tr is a command in Unix, Plan 9, Inferno, and Unix-like operating systems. It is an abbreviation of translate or transliterate, indicating its operation of replacing or removing specific characters in its input data set.
In computing, cp is a command in various Unix and Unix-like operating systems for copying files and directories. The command has three principal modes of operation, expressed by the types of arguments presented to the program for copying a file to another file, one or more files to a directory, or for copying entire directories to another directory.
split is a utility on Unix, Plan 9, and Unix-like operating systems most commonly used to split a computer file into two or more smaller files.
In computing, umask is a command that determines the settings of a mask that controls how file permissions are set for newly created files. It may also affect how the file permissions are changed explicitly. umask is also a function that sets the mask, or it may refer to the mask itself, which is formally known as the file mode creation mask. The mask is a grouping of bits, each of which restricts how its corresponding permission is set for newly created files. The bits in the mask may be changed by invoking the umask command.
Most file systems include attributes of files and directories that control the ability of users to read, change, navigate, and execute the contents of the file system. In some cases, menu options or functions may be made visible or hidden depending on a user's permission level; this kind of user interface is referred to as permission-driven.
In Unix-like and some other operating systems, find is a command-line utility that locates files based on some user-specified criteria and either prints the pathname of each matched object or, if another action is requested, performs that action on each matched object.
rm is a basic command on Unix and Unix-like operating systems used to remove objects such as computer files, directories and symbolic links from file systems and also special files such as device nodes, pipes and sockets, similar to the del command in MS-DOS, OS/2, and Microsoft Windows. The command is also available in the EFI shell.
In computing, the sticky bit is a user ownership access right flag that can be assigned to files and directories on Unix-like systems.
In computing, tee is a command in command-line interpreters (shells) using standard streams which reads standard input and writes it to both standard output and one or more files, effectively duplicating its input. It is primarily used in conjunction with pipes and filters. The command is named after the T-splitter used in plumbing.
In computing, sort is a standard command line program of Unix and Unix-like operating systems, that prints the lines of its input or concatenation of all files listed in its argument list in sorted order. Sorting is done based on one or more sort keys extracted from each line of input. By default, the entire input is taken as sort key. Blank space is the default field separator. The command supports a number of command-line options that can vary by implementation. For instance the "-r" flag will reverse the sort order.
In computing, a hidden folder or hidden file is a folder or file which filesystem utilities do not display by default when showing a directory listing. They are commonly used for storing user preferences or preserving the state of a utility and are frequently created implicitly by using various utilities. They are not a security mechanism because access is not restricted – usually the intent is simply to not "clutter" the display of the contents of a directory listing with files the user did not directly create.
A command-line interface (CLI) is a means of interacting with a device or computer program with commands from a user or client, and responses from the device or program, in the form of lines of text. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods.
