CSC322 C Programming and UNIX - Department of Computer ...

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Hackers! Hacker [originally, someone who makes furniture with an axe] 1. A person who enjoys exploring the details of programmable systems and how to stretch their capabilities, as opposed to most users, who prefer to learn only the minimum necessary. 2. One who programs enthusiastically (even obsessively) or who enjoys programming rather than just theorizing about programming. 3. A person capable of appreciating hack value. 4. A person who is good at programming quickly. 5. An expert at a particular program, or one who frequently does work using it or on it; as in ‘a Unix hacker’. (Definitions 1 through 5 are correlated, and people who fit them congregate.) 6. An expert or enthusiast of any kind. One might be an astronomy hacker, for example. 7. One who enjoys the intellectual challenge of creatively overcoming or circumventing limitations. 8. [deprecated] A malicious meddler who tries to discover sensitive information by poking around. Hence ‘password hacker’, ‘network hacker’. The correct term for this sense is cracker. The New Hacker’s Dictionary (aka the Jargon File) Stephan Schulz 2
The UNIX Operating System UNIX and You Stephan Schulz 3
Page 1: CSC322 C Programming and UNIX Steph
Page 5 and 6: The UNIX Operating System UNIX and
Page 7 and 8: UNIX is a big-iron operating system
Page 9 and 10: UNIX First portable operating syste
Page 11 and 12: UNIX history tree (simplified) For
Page 13 and 14: 1978 3BSD, adding virtual memory 19
Page 15 and 16: A Short History of UNIX and C 1991
Page 17 and 18: Another Opinion UNIX is not an oper
Page 19 and 20: Upshot You don’t have to grow a b
Page 21 and 22: Shell UNIX Architecture Libraries U
Page 23 and 24: Some Concepts UNIX is a multi-user
Page 25 and 26: UNIX: Provide Tools, Not Policy The
Page 27 and 28: Default KDE Desktop (SuSE Linux) St
Page 29 and 30: KDE Desktop with Terminal Applicati
Page 31 and 32: Text Interface Example (contd.) Mos
Page 33 and 34: Typical File System Layout / (Root
Page 35 and 36: More about files We can use the -l
Page 37 and 38: GNU info files UNIX Online Document
Page 39 and 40: CSC322 C Programming and UNIX UNIX
Page 41 and 42: Command Types There are different t
Page 43 and 44: UNIX User Commands: rm, mkdir, rmdi
Page 45 and 46: Effective Shell Use: Editing/Comple
Page 47 and 48: Example: File Handling and Globbing
Page 49 and 50: UNIX User Commands: cat/more/less c
Page 51 and 52: Getting into it: vi vi flyby Modal
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Emacs for Everyone Getting into it:
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Emacs for Everyone III Emacs is non
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ed is the standard text editor When
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? ? quit ? exit ? bye ? hello? ? ea
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SO-CALLED "VISUAL" EDITORS HAVE BEE
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Usage: grep . . . UNIX User Comma
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Simple Output Redirection You can r
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Input Redirection You can also redi
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Basic Process Control You can start
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Job Control Example $ emacs & (Star
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CSC322 C Programming and UNIX Progr
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Consider the following C program #i
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#include #include int main(void)
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A Closer Look (4) gcc is the GNU C
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The Fahrenheit-Celsius Example Comp
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Variables “int fahrenheit, celsiu
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A while-loop has the form while()
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UNIX User Commands: cp and mv cp wi
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Flow-Control: if The primary means
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Flow-Control: for The for-loop in C
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for vs. while Note that for is more
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Types: Integers and Characters C ha
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Simple Character I/O The C library
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Exercises Write a programm that con
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Nomination: Most Useless Use of cat
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Example: Word Counting /* Count wor
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Another View at Expressions Express
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Expressions: Associativity of Binar
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Expressions: Logical Operators Logi
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Floating Point Numbers C supports t
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Administrative Notes Please ssh to
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#include #include #include int m
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Initializing Arrays In the example,
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No Safety Belts and No Air Bag! C d
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Functions Functions are the primary
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Function Calling A function is call
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Example: Printing Character Frequen
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Assignment A prime number is a (pos
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A function is a named subroutine Re
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Example: int read int10(void) /* We
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Do we have a Valid Digit? /* Is a c
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Build General Functions! Good progr
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Example: Printing Integers We now w
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Writing a Number in any Base (
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Putting Things Together: A Base Con
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Usage Example $ ./base converter In
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Includes Translates into Is combibe
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The C Preprocessor The C preprocess
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myfile.c: A Poem #include "mary" $
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Simple Macro Definitions: #define T
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Macros with Arguments Macro definit
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#define Caveats Since macros work b
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cond preproc.c: #define hallo #defi
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cond preproc.c: #define hallo #defi
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Combinations of #ifdef and #include
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Definitions and Declarations Defini
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Scoping Rules There are two kinds o
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Limiting Potential Scope By default
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Persistent Local Variables: static
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Example: Static and Automatic Varia
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Implement the libray in its own sou
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Project: An RPN Calculator Aim: A c
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$ ./rpn calc Usage Example 10 8 + S
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Subtasks From the above, we can ide
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The Character I/O Library: Ideas Ma
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The Character I/O Library: Global V
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int LookChar(void) { int c = GetCha
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#include "chario.h" The Integer I/O
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The Integer I/O Library: Helper fun
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The Integer I/O Library: Helper fun
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The Integer I/O Library: Checking f
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Exercises Download the program from
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Recapitulation: Some of our Library
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Case Distinctions Note: The operato
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The Stack Abstract Datatype A stack
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Pushing things onto the stack: PUSH
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The Main Program: Prelimaries and D
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The Main Loop: Arithmetic operators
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The Main Loop: I/O operators switch
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case ’S’: for(i=0; i
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UNIX User Commands: dc dc is an arb
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Bitwise Operators Bitwise operators
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Example These macros can be used to
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Conditional Expressions Similarly t
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Type Conversion (Casting) As alread
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Order Of Execution In general, the
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Types in C C offers a set of basic
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Defining New Types with typedef The
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Enumerations in C Enumeration data
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enum and typedef Typically, enumera
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Aggregating Data Types Let’s agai
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Consider the following definition:
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Exercises Create a function that ha
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Assume the following problem: Repre
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typedef enum { circle, square, rect
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typedef union { CircleCoord circle_
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Pointers Pointers are derived types
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#include #include void swap(int *
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Why Pointers? The are two main reas
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Exercises Write a program that prin
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Refresher: Pointers A pointer type
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The malloc() function We request a
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More on Dynamic Memory Allocation G
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Example: SecureMalloc() Note: In my
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Example: Linear Lists (of Integers)
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#ifndef INT_LISTS #define INT_LISTS
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Example - Inserting At the End /* I
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Example - Freeing Lists /* Free the
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Example - Main Function int main(vo
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Use this datatype and the functions
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Monday, Oct. 14th, 11:00 - 11:50 To
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Refresher: Dynamic Memory Handling
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int array[10]; int *a, *b; a = arra
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Compiling: gcc -o csc322 csc322.c R
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#include #include #include void
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CSC322 C Programming and UNIX Midte
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The File System / (Root directory)
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Some Important UNIX Commands (1) Or
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Input and Output Redirection, Pipin
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C Compiling with gcc Programs consi
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if...else - Conditional execution s
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C Preprocessor The #include directi
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#include #include #define BUF_SIZ
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Example: Growing the Buffer as Need
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char *cp, *cq; int *ip, *iq; Pointe
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Reading the Command Line: argc and
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#include #include Example: Echoin
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CSC322 C Programming and UNIX Makin
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chario.h The rpn calc Example (Simp
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UNIX User Utilities: make make is a
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Built-In Rules and Makefile Variabl
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Phony Targets Not all targets need
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CSC322 C Programming and UNIX Odds
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Assertions Internal consistency che
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#include #include #include int g
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Search in Loops A frequent use of l
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Selective Operations and Special Ca
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do/while Loops Both while and for l
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E theorem prover Some Loop Statisti
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CSC322 C Programming and UNIX Funct
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Function Pointers We can use the ad
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Example #include #include int add
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C Library Functions: qsort() qsort(
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#include #include Example typedef
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Unsorted: 103 70 105 115 81 127 74
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C Standard Library Organisation - a
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#include #include #include #incl
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CSC322 C Programming and UNIX C Sta
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Some C Character Classes All charac
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#include #include #include int m
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Strings Strings are not part of the
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Example: Duplicating Strings Severa
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String Functions from (3) int strc
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Generic Memory Access Functions The
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Memory Functions from (2) void *me
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Memory Functions from (1) void *me
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Example #include #include #includ
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Input and Output in the Standard Li
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Opening File Streams In addition to
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Simple Stream Based I/O Functions (
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} for(i=1; i
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Exercises Write a version of memmov
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Remark about fgets() char *fgets(ch
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int main(int argc, char *argv[]) {
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$ man man | ./mycat1 Example Output
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Buffering and Flushing Both input a
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#include #include int main(int ar
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More Operations on Files int remove
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Error Functions Each FILE data stru
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A first Example printf("%d divided
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Format Specifiers Format specifiers
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Some Conversion Letters (2) f: Prin
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Size Modifiers Size modifiers are u
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The Flags -: Left-justify output (o
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#include #include Example int mai
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$ arch322 Makefile sort_csc322.c ut
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Processes A UNIX process is an inst
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$ ps PID TTY TIME CMD 1125 pts/3 00
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$ ps aux Interesting ps Example USE
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Signals Signals are a way to signal
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Some UNIX Signals UNIX defines abou
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top is an interactive version of ps
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Catching Signals User programs can
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ANSI C Signal Handling with signal.
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ANSI C Signal Handers A signal hand
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int main(int argc, char* argv[]) {
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Exercises Start a long running proc
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UNIX philosophy: Everything is a fi
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FIFOs (named pipes) UNIX File Types
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The stat() Functions (2) All three
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} Example Continued else if(S_ISLNK
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Example Output (of device directory
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Links (2) Soft links create indirec
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Exercises Read man stat and extend
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All files have an owner (a user) Fi
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User Groups Groups are used in UNIX
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UNIX User Utilities: chown and chgr
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Symbolic Encoding ls -l prints a st
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Examples rw-r--r-- is the most comm
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chmod Examples chmod ugo+rwx myfile
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Exercises Read the man and info pag
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File Decriptors Files are identifie
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Option flags for open() Note: All o
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Notes on open() and close() The mod
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} Example Continued while((count =
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Cheating with fdopen() Formatted, b
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CSC322 C Programming and UNIX More
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FILE* myfile Standard IO Library Th
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Manipulating File Descriptors: fcnt
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if(flags & O_APPEND) { printf("Appe
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Multiplexing I/O Often, a program h
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select() Arguments fd set is define
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$ ./select_example 2 file descripto
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CSC322 C Programming and UNIX Basic
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Networking Stephan Schulz 517
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Networking Concepts Is communicatio
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Level 2 protocol (Hardware-Agnostic
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The Transmission Control Protocol (
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A server offers a certain service C
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The Client Side for TCP Connections
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Creating Sockets with socket() (2)
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Socket Adresses for IPv4 For IPv4 a
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Connecting to a Remote Port: connec
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Example (2) sock = socket(PF_INET,
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The Server Side A server has a more
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Naming a Socket (Binding a Socket t
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Accepting Connections To finally es
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Example (2) if(argc!=2) { fprintf(s
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man pages: - man socket - man 2 bin
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CSC322 C Programming and UNIX Proce
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Process Properties For each process
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Exiting There are three normal ways
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Cleaning up: atexit() ANSI C allows
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Example (2) int main(void) { if(ate
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Running other Programs: system() Th
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Termination Status Interpretation T
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Example: Executing Commands int mai
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Exercises Write a program that prin
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Creating new Processes: fork() The
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} Example if(child_pid == 0) { pid
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Comments on fork() Order of executi
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#include int main(int argc, char*
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FILE* myfile Standard IO Library I/
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Example: Bufferd I/O and Forking /*
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Waiting for Children to Die As stat
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Example (2) for(i=0; i
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Output: Example Output Parent. My P
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CSC322 C Programming and UNIX Proce
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Getting and Changing Process Groups
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Example (2) res = setpgid(0,0); if(
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Example Output $ ./pg example Paren
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Is this good for Something? There a
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Example (2) pid = getpid(); pgid =
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Example Output with kill Queen bee:
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Waiting for Termination: waitpid()
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Exercises Write a program that keep
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Process Environment Each UNIX proce
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$ printenv Example: Part of my Envi
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Accessing the Environment from a Pr
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The POSIX Interface to the Environm
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The 6 exec Functions #include int
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int count_words(char* line) { int w
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} Example (5) for(i=0; i
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int main(void) { pid_t child_pid; c
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} { /* Parent */ setpgid(child_pid,
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# ls * Command: ls Arguments: ls *
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CSC322 C Programming and UNIX Final
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Pointers and Dynamic Arrays Arrays
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New Flow Control Constructs break i
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Standard Library: Characters and St
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Standard Library: Buffered I/O Stan
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Processes and Signals Processes are
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UNIX: Everything is a file File typ
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File Descriptors and select() File
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TCP/IP (v4) Connections Reliable, s
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Process Environment and Program Exe
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