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Linux Guide - S

  • sendmail
    Sendmail sends a message to one or more recipients, routing the message over whatever networks are necessary. Sendmail does inter-network forwarding as necessary to deliver the message to the correct place. Sendmail is not intended as a user interface routine; other programs provide user-friendly front ends; sendmail is used only to deliver pre-formatted messages.
  • Samba
    a suite of programs which work together to allow clients to access to a server's filespace and printers via the SMB (Session Message Block) protocol. This means that you can redirect disks and printers to Unix disks and printers from Lan Manager clients, Windows for Workgroups 3.11 clients, Windows NT clients, Linux clients and OS/2 clients
  • Scheme
    A small, uniform Lisp dialect with clean semantics, developed initially by Guy Steele and Gerald Sussman in 1975. Scheme uses applicative order reduction and is lexically scoped. It treats both functions and continuations as first-class objects
  • search path
    A list of directories in which a given user's commands may be found. Each time the user enters a command at the keyboard, the shell searches the list to find the command. You can execute only those commands that belong to the directories in your search path
  • segmentation fault
    An error in which a running program attempts to access memory not allocated to it and core dumps with a segmentation violation error
  • Serif
    Little hooks on the ends of characters. For example, the letter i in a font such as Times Roman has serifs protruding from the base of the i and the head of the i. Serif fonts are usually considered more readable than fonts without serifs. There are many different types of serif fonts
  • server
    A program which provides some service to other (client) programs. The connection between client and server is normally by means of message passing, often over a network, and uses some protocol to encode the client's requests and the server's responses
  • session
    One complete interaction between a user and the Linux system, from login to logout
  • setuid
    sets the effective user ID of the current process. If the effective userid of the caller is root, the real and saved user ID's are also set.
  • SGID
    Set Group ID: a file attribute which allows a program to run with specific group privileges no matter who executes it
  • shared library
    A library where the linker leaves a note in the output that says "when this is run, it will first have to load this library". Shared libraries tend to make for smaller executables than static library. On Linux they have names like
  • shared memory
    memory which can be access by more than one process in a multitasking operating system with memory protection
  • Shared memory pixmaps
    They are 2 dimensional arrays of pixels in a format specified by the X server, where the pixmap data is stored in the shared memory segment. See MIT-SHM.
  • shareware
    Commercial software which allows a free limited trial. xv is a popular shareware Linux graphics program
  • shell
    a utility program that enables the user to interact with the UNIX operating system. Commands entered by the user are passed by the shell to the operating system which carries them out. The results are then passed back by the shell and displayed on the user's display
  • shell prompt
    a character at the start of the command line which indicates that the shell is ready to receive your commands. The character is usually a '%' (percent sign) or a $ (dollar sign). It may be different on your system
  • shell script
    A program written to be interpreted by the shell of an operating system such as Linux
    Secure hypertext transfer protocol - developed by Enterprise Integration Technologies to ensure security with commercial transactions on the Internet
  • shutdown
    brings the system down in a secure way. All logged in users are notified that the system is going down, and login(1) is blocked. It is possible to shut the system down immediately, or after a delay. All processes are first notified that the system is going down by the signal SIGTERM. This gives programs like vi(1) the time to save the file being edited, mail and news processing programs a chance to exit cleanly, etc. Shutdown does its job by signalling the init process, asking it to change the runlevel. Runlevel 0 is used to halt the system, runlevel 6 is used to reboot the system and runlevel 1 is used to put to system into a state where administrative tasks can be performed
  • Signals
    used to inform processes of unexpected external events such as a time out or forced termination of a process. A signal consists of prescribed message with a default action embedded in it. Each signal has a unique number associated with it. An example is SEGV, segmentation violation
  • single user mode
    a system mode created for administrative and maintenance activities demand complete control of the system. When the system is in this state whoever is logged in becomes root. This is however, a minimal system startup state. Only the root partition is mounted so only commands that reside in the root filesystem are available
  • slash
    The / character Linux uses in path names. A / by itself, or at the beginning of a pathname, means the root directory of the file system. Slashes are used also between one directory name and the next, and between the directory name and the filename in long path names
  • sleep
    Pertaining to a UNIX process, to suspend execution until some event takes place or for a specific period of time. Processes automatically sleep while waiting for results from peripherals
  • SLI mode
    SLI means "Scanline Interleave"In this mode, two Pixelfx are connected and render in alternate turns, one handling odd, the other handling even scanlines of the actual output.
  • SLIP
    Serial Line Internet Protocol - A communication method that allows a personal computer to connect directly to the Internet using a standard telephone line
  • Smalltalk
    a popular object-oriented programming language
  • smp
    Symmetric Multi-Processing
  • SMP machines
    Shared memory machines that communicate through memory.
  • smrsh
    SendMail Restricted SHell: the shell that Sendmail uses to execute programs. smrsh puts restrictions on the programs that can be run to make it safer than using a regular shell such as the Bourne Shell
  • SNMP
    Simple Network Management Protocol. An Internet protocol. Allows nodes to determine which services another nodes offer
  • sorting
    Rearranging a list of items in a prescribed order. The Linux sort command lets you sort information in a variety of different ways.
  • source code
    The form in which a computer program is written by the programmer. Source code is written in some formal programming language which can be compiled automatically into object code or machine code or executed by an interpreter
  • Sourcing a File
    The lines of code in the file are executed as if they were printed at the command line.
  • spam
    flooding the Internet with many copies of the same message, in an attempt to force the message on people who would not otherwise choose to receive it. Most spam is commercial advertising, often for dubious products, get-rich-quick schemes, or quasi-legal service
  • spawn
    to create a child process in a multitasking operating system. Eg. Linux's fork system call
  • split
    Creates one or more output files (as many as necessary) containing consecutive sections of the infile, or the standard input if none is given or the name `-' is given. By default, split puts 1000 lines of the input file, or whatever is left if it is less than that, into each output file.
  • spool
    Simultaneous Peripheral Operation On-Line - To send files to some device or program (a `spooler') that queues them up and does something useful with them later
  • SQL
    Structured Query Language is a language for manipulating data in relational databases. It has a very simple grammar and is a standard with wide industry support. SQL-based databases have become the core of the classical client/server database concept
  • ssh
    A standard for cryptographic connections over a TCP connection
  • SSL
    Secure Sockets Layer - A protocol designed by Netscape to enable encrypted, authenticated communications across the Internet
  • Stallman, Richard
    The founder of the GNU project, launched in 1984 to develop the free operating system GNU (an acronym for GNU's Not Unix''), and thereby give computer users the freedom that most of them have lost. GNU is free software: everyone is free to copy it and redistribute it, as well as to make changes either large or small. Richard Stallman is the principal author of the GNU C Compiler, a portable optimizing compiler which was designed to support diverse architectures and multiple languages. The compiler now supports over 30 different architectures and 7 programming languages. Stallman also wrote the GNU symbolic debugger (GDB), GNU Emacs, and various other GNU programs.
  • standard input
    the source of information for a command. This is assumed to be the keyboard unless input is redirected or piped from a file or another command.
  • standard output
    the destination for information from a command. This is assumed to be the terminal display unless ouput is redirected or piped to a file or another command
  • static library
    A library where the code needed by the program modules are copied directly into the executable output file. On Linux, static libraries have names like libname.a. They make for larger executables than a shared library
  • steganography
    The practice of hiding one piece of information inside of another. The most common example is watermarking
  • string
    In computer usage in general, a sequence of characters
  • SUID
    Set User ID: a file attribute which allows a program to run as a specific user no matter who executes it
  • superuser
    An informal name for root.
  • swap
    to move information from a fast-access memory to a slow-access memory (`swap out'), or vice versa (`swap in'). Often refers specifically to the use of disks as `virtual memory'
  • swap space
    Storage space, especially temporary storage space used during a move or reconfiguration
  • symbolic link
    A special type of Unix file which refers to another file by its pathname. A symbolic link is created with the "ln" (link) command
  • symmetric key cryptography
    A cryptography system in which both parties have the same encryption key, as in secret key cryptography.
  • sync
    To force all pending I/O to the disk
  • syslog
    The UNIX System Logger
  • system call
    The mechanism used by an application program to request service from the operating system. System calls often use a special machine code instruction which causes the processor to change mode (e.g. to "supervisor mode" or "protected mode")

Key:  Commands - People - General

Last Updated Saturday, December 04 2004 @ 11:15 AM EST

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