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

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Moving Through the File System We can use the command cd to change our working directory: [schulz@gettysburg ∼]$ pwd /lee/home/graph/schulz cd / [schulz@gettysburg /]$ pwd / [schulz@gettysburg /]$ cd bin [schulz@gettysburg /bin]$ pwd /bin [schulz@gettysburg /bin]$ cd /lee/home/graph/schulz [schulz@gettysburg ∼]$ pwd /lee/home/graph/schulz Each directory contains two special entries: . and .. – . represents the directory itself. cd . is a NOP – .. normally represents the parent directory. cd .. moves the working directory up one level. In /, .. points to / itself Stephan Schulz 34
More about files We can use the -l (“long format”) option to ls to show us all all attributes [schulz@gettysburg ∼]$ ls -l -rw------- 1 schulz users 1531904 Aug 29 10:55 core drwxr-xr-x 3 schulz users 4096 Aug 29 10:55 Desktop The long format of ls shows us more about the files: – The first letter tells us the file type. d is a directory, - means a plain file – The next nine letters describe access rights, i.e. who is allowed to read, write, and execute the file. More on those later! – The next number is the number of (hard) links to a file. More on that much later! – Next is the user that owns the file – After that, the group that owns the file – Next comes the file size in bytes – Then the date the file was changed for the last time – Finally, the name of the file Stephan Schulz 35
Page 1 and 2: CSC322 C Programming and UNIX Steph
Page 3 and 4: The UNIX Operating System UNIX and
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: Typical File System Layout / (Root
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
Page 53 and 54: Emacs for Everyone Getting into it:
Page 55 and 56: Emacs for Everyone III Emacs is non
Page 57 and 58: ed is the standard text editor When
Page 59 and 60: ? ? quit ? exit ? bye ? hello? ? ea
Page 61 and 62: SO-CALLED "VISUAL" EDITORS HAVE BEE
Page 63 and 64: Usage: grep . . . UNIX User Comma
Page 65 and 66: Simple Output Redirection You can r
Page 67 and 68: Input Redirection You can also redi
Page 69 and 70: Basic Process Control You can start
Page 71 and 72: Job Control Example $ emacs & (Star
Page 73 and 74: CSC322 C Programming and UNIX Progr
Page 75 and 76: Consider the following C program #i
Page 77 and 78: #include #include int main(void)
Page 79 and 80: A Closer Look (4) gcc is the GNU C
Page 81 and 82: The Fahrenheit-Celsius Example Comp
Page 83 and 84: 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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CSC322 C Programming and UNIX Progr
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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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#include #include int main(void)
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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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