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Stand-alone Shell
Stand-alone shell (sash) is a Unix shell designed for use in recovering from certain types of system failures and errors. The built-in commands of sash have all libraries linked statically, so unlike most shells on Linux, the standard UNIX commands do not rely on external libraries. For example, the copy command (cp) requires libc.so and ld-linux.so when built from GNU Core Utilities on Linux. If any of these libraries get corrupted, the coreutils cp command would not work; however, in sash, the built-in command, cp, would be unaffected. In earlier times, most critical commands (including shells) in /sbin or even /bin were statically linked for this purpose, whereas in /usr/sbin and /usr/bin you would find the more feature-rich versions that were dynamically linked. This is not common anymore and as such, statically linked shells with built-in commands have become more important. Sash has the following built-in commands: : ar, chattr, chgrp, chmod, chown, cmp, cp, dd, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Screenshot
A screenshot (also known as screen capture or screen grab) is an analog or digital image that shows the contents of a computer display. A screenshot is created by a (film) camera shooting the screen or the operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ... or software running on the device powering the display. Screenshot techniques Digital techniques The first screenshots were created with the first interactive computers around 1960. Through the 1980s, computer operating systems did not universally have built-in functionality for capturing screenshots. Sometimes text-only screens could be dumped to a text file, but the result would only capture the content of the screen, not the appearance, nor were graphics screens preservable this way. Some systems had a BS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dd (Unix)
dd is shell command for reading, writing and converting file data. Originally developed for Unix, it has been implemented on many other environments including Unix-like operating systems, Windows, Plan 9 and Inferno. The command can be used for many purposes. For relatively simple copying operations, it tends to be slower than domain-specific alternatives, but it excels at overwriting or truncating a file at any point or seeking in a file. The command supports reading and writing files, and if a driver is available to support file-like access, the command can access devices too. Such access is typically supported on Unix-based systems that provide file-like access to devices (such as storage) and special device files (such as /dev/zero and /dev/random). Therefore, the command can be used for tasks such as backing up the boot sector of a drive, and obtaining random data. The command can also support converting data while copying; including byte order swapping and conve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mknod
In Unix-like operating systems, a device file, device node, or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions. Overview Device files usually provide simple interfaces to standard devices (such as printers and serial ports), but can also be used to access specific unique resources on those devices, such as disk partitions. Additionally, device files are useful for accessing system resources that have no connection with any actual device, such as data sinks and random number generators. There are two general kinds of device files in Unix-like operating systems, k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mkdir
(make directory) command (computing), command in the Unix, DOS, Digital Research, DR FlexOS, IBM OS/2, Microsoft Windows, and ReactOS operating systems is used to make a new directory (file systems), directory. It is also available in the Unified Extensible Firmware Interface, EFI shell and in the PHP scripting language. In DOS, OS/2, Windows and ReactOS, the command is often abbreviated to md. The command is analogous to the Stratus Technologies, Stratus Stratus VOS, OpenVOS create_dir command. MetaComCo TRIPOS and AmigaDOS provide a similar MakeDir command to create new directories. The numerical analysis, numerical computing environments MATLAB and GNU Octave include an mkdir function with similar functionality. History In early versions of Unix (Berkeley Software Distribution, 4.1BSD and early versions of System V), this command had to be setuid superuser, root as the kernel (operating system), kernel did not have an mkdir syscall. Instead, it made the directory with mknod a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ln (Unix)
is a shell command for creating a link file to an existing file or directory. By default, the command creates a hard link, but with the command line option, it creates a symbolic link. Most systems disallow a hard link to a directory since such links could disrupt the structure of a file system and interfere with the operation of other utilities. The command can create a symbolic link to non-existent file. The command appeared in Issue 2 of the X/Open Portability Guidelines. The version in GNU Core Utilities was written by Mike Parker and David MacKenzie. The command is available in Windows via UnxUtils and has been ported to IBM i. Links A link allows more than one path to refer to the same file. A hard link is a directory entry that refers to a file's inode (an internal reference). A file can have multiple hard links each referring to the same inode. Creating a hard link does not copy the contents of the file; but merely causes another name to be associated with the sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Losetup
In Unix-like operating systems, a loop device, vnd (vnode disk), or lofi (loop file interface) is a pseudo-device that makes a computer file accessible as a block device. Before use, a loop device must be connected to an existent file in the file system. The association provides the user with an application programming interface (API) that allows the file to be used in place of a block special file (cf. device file system). Thus, if the file contains an entire file system, the file may then be mounted as if it were a disk device. Files of this kind are often used for CD ISO images and floppy disk images. Mounting a file containing a file system via such a loop mount makes the files within that file system accessible. They appear in the mount point directory. A loop device may allow some kind of data elaboration during this redirection. For example, the device may be the unencrypted version of an encrypted file. In such a case, the file associated with a loop device may be anoth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kill (command)
In computing, kill is a command that is used in several popular operating systems to send signals to running processes. Implementations Unix and Unix-like In Unix and Unix-like operating systems, kill is a command used to send a signal to a process. By default, the message sent is the termination signal, which requests that the process exit. But ''kill'' is something of a misnomer; the signal sent may have nothing to do with process killing. The kill command is a wrapper around the kill() system call, which sends signals to processes or process groups on the system, referenced by their numeric process IDs (PIDs) or process group IDs (PGIDs). kill is always provided as a standalone utility as defined by the POSIX standard. However, most shells have built-in kill commands that may slightly differ from it. There are many different signals that can be sent (see ''signal'' for a full list), although the signals in which users are generally most interested are SIGTERM (" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gzip
gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from which the "g" of gzip is derived). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993. The decompression of the ''gzip'' format can be implemented as a streaming algorithm, an important feature for Web protocols, data interchange and ETL (in standard pipes) applications. File format gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of the compress utility and other popular archivers. "gzip" also refers to the gzip file format (described in the table below). In sho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Find (Unix)
In Unix-like 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. It initiates a search from a desired starting location and then recursively traverses the nodes (directories) of a hierarchical structure (typically a tree). find can traverse and search through different file systems of partitions belonging to one or more storage devices mounted under the starting directory. The possible search criteria include a pattern to match against the filename or a time range to match against the modification time or access time of the file. By default, find returns a list of all files below the current working directory, although users can limit the search to any desired maximum number of levels under the starting directory. The related locate programs use a database of indexed files obtained thro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File (command)
file is a shell command for reporting the type of data contained in a file. It is commonly supported in Unix and Unix-like operating systems. As the command uses relatively quick-running heuristics to determine file type, it can report misleading information. The command can be fooled, for example, by including a magic number in the content even if the rest of the content does not match what the magic number indicates. The command report cannot be taken as completely trustworthy. The Single UNIX Specification (SUS) requires the command to exhibit the following behavior with respect to the file specified via the command-line: # If the file cannot be read, or its Unix file type is undetermined, the command will report that the file was processed but its type was undetermined # The command must be able to determine the types directory, FIFO, socket, block special file, and character special file # A zero-length file is reported as such # An initial part of file is considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grep
grep is a command-line utility for searching plaintext datasets for lines that match a regular expression. Its name comes from the ed command g/re/p (global regular expression search and print), which has the same effect. grep was originally developed for the Unix operating system, but later became available for all Unix-like systems and some others such as OS-9. History Before it was named, grep was a private utility written by Ken Thompson to search files for certain patterns. Doug McIlroy, unaware of its existence, asked Thompson to write such a program. Responding that he would think about such a utility overnight, Thompson actually corrected bugs and made improvements for about an hour on his own program called "s" (short for "search"). The next day he presented the program to McIlroy, who said it was exactly what he wanted. Thompson's account may explain the belief that grep was written overnight. Thompson wrote the first version in PDP-11 assembly language to help Le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
