Cs288 Intensive Programming in Linux Instructor: C F Yurkoski Christopher.f.yurkoski@njit.edu Section web site: https://web.njit.edu/~yurkowsk/cs288.html Class 6 6-9-15

Topics today Homework revu More C Time for questions

text 6-9-15 cfy

Submit only .c files (or .h if I ask for header files too.) Insure that your code compliles on the afs Linux using the default options (no –gcc) Write a hello world program – done in class last week Do problem 1-4 from text Do problem 1-8 from text

First program /* This is a comment */ #include <stdio.h> /* preproc d*/ main() { printf("hello world\n"); } 6-9-15

Problem 1-4 Exercise 1-4. Write a program to print the corresponding Celsius to Fahrenheit table. https://web.njit.edu/~yurkowsk/x/problem1-4.c

Problem 1-8: ite a program to count blanks, tabs, and newlines. ./public_html/x/exer1-8A.c

Some more Basics of C 6-9-15

Conditional Operator ? : exp1 ? exp2 : exp3 If exp1 is non-zero value of expression is exp2 otherwise it is exp3 1 ? 2 : 3 6-9-15 cfy

Operator Precedence left to right * / % + - 6-9-15 cfy

Some Basics /* Comments */ { blocks } Parameters ( ) # preprocessor directive Statements end with ; Loops: for while Conditionals if then 6-9-15

$ cat header. h #define ROOT 1 $ cat main1. c /. This is a multi-line $ cat header.h #define ROOT 1 $ cat main1.c /* * This is a multi-line * comment block. */ #include <srdio.h> #include "header.h" /* This a one line comment */ main(){ int x=ROOT; /* this is an embeeded comment */ #ifdef ROOT printf("%d",x); #else printf("not root\n"); #endif }

$ cc main1.c $ ./a.out 1$

Basic printf formats %i or %d int %c char %f float %s string 6-9-15 cfy

Width and precision %d print as decimal integer at least 6 characters wide %f print as floating point %6f print as floating point, at least 6 characters wide %.2f print as floating point, 2 characters after decimal point 6-9-15 cfy

I/O C=getchar(); putchar(C); 6-9-15 cfy

for statement for(init;condition;increment) { statement(s); } for(i=0;i<5;i++) printf(“%d\n”,i); 6-9-15 cfy

Symbolic Contants #define name replacement text #define LIMIT 30 6-9-15 cfy

Escape sequences \a 07 Alarm (Beep, Bell) \b 08 Backspace \f 0C Formfeed \n 0A Newline (Line Feed) \r 0D Carriage Return \t 09 Horizontal Tab \v 0B Vertical Tab \\ 5C Backslash \‘ 27 Single quotation mark \“ 22 Double quotation mark \? 3F Question mark \nnn any The character whose numerical value is given by nnn interpreted as an octal number \xhh any The character whose numerical value is given by hh interpreted as a hexadecimal number 6-9-15

if statement if ( expression) statement else if ( expression ) else if ( expression ) 6-9-15 cfy

arrays int myarray[10]; 6-9-15 cfy

functions int function ( int param1, char param2); … int function ( int param1, char param2) { int local1, local2; /* call by value */ retval=function2 (local1); return(10); } 6-9-15 cfy

argv, argc #include <stdio.h> int main (int argc, char *argv[]) { printf(“%s\n”,argv[0]); return 0; } 6-9-15 cfy

compiler cc file.c –o file 6-9-15 cfy

More basic C More on arrays: Array initialization during declaration: int num[5]; num[0]=1; int num[5]={1,2,3,4,5}; 6-9-15 cfy

Multi-dimensional arrays int a[2][3]; int a[2][3]={{1,2,3},{4,5,6}}; 6-9-15 cfy

Multi-dimensional arrays cont #include <stdio.h> main() { int a[2][3]={{1,2,3},{4,5,6}}; int i,j; for(i=0;i<2;i++) for(j=0;j<3;j++) printf("a[%d][%d]=%d\n",i,j,a[i][j]); } 6-9-15 cfy

Multi-dimensional arrays cont afsconnect1-58 >: ./a.out a[0][0]=1 a[0][1]=2 a[0][2]=3 a[1][0]=4 a[1][1]=5 a[1][2]=6 6-9-15 cfy

Strings are just arrays of characters. #include <stdio.h> main() { char name1[25]="NJIT"; char name2[25]={'N','J','I','T','\0'}; printf("name1=%s\n",name1); printf("name2=%s\n",name2); } >: ./a.out name1=NJIT name2=NJIT 6-9-15 cfy

Strings (cont). main() { char name1[25]="NJIT"; char name2[25]={'N','J','I','T','\0'}; char *name3="NJIT"; printf("name1=%s\n",name1); printf("name2=%s\n",name2); printf("name3=%s\n",name3); } afsconnect1-67 public_html >: ./a.out name1=NJIT name2=NJIT name3=NJIT 6-9-15 cfy

Strings (cont). Header file string.h Some examples: strcmp String Compare strcat String Concatenation memcpy Copy Memory Block strlen String Length 6-9-15 cfy

General form: Strcat(string1,string2) Appends string2 to string1; Strings (cont). General form: Strcat(string1,string2) Appends string2 to string1; 6-9-15 cfy

Addresses! & used to get the address of a variable main() { int i=666; printf("i= %d\n",i); printf("&i= %d\n",&i); } afsconnect1-72 public_html >: ./a.out i= 666 &i= 1814055836 6-9-15 cfy

More C keywords switch break, continue, goto sizeof Storage classes: auto register extern static 6-9-15 cfy

switch( Grade ) { case 'A' : printf( "Excellent\n" ); case 'B' : printf( "Good\n" ); case 'C' : printf( "OK\n" ); case 'D' : printf( "Mmmmm....\n" ); case 'F' : printf( "You must do better than this\n" ); default : printf( "What is your grade anyway?\n" ); } 6-9-15 cfy

label: while (true) { if(a) break; if(b) continue; if(c) goto label; } 6-9-15 cfy

printf("sizeof i= %d\n",sizeof(i)); printf("sizeof array= %d\n", main() { int i=666; char array[15]; double n; printf("sizeof i= %d\n",sizeof(i)); printf("sizeof array= %d\n", sizeof(array)); printf("sizeof n= %d\n", sizeof(n)); } >: ./a.out sizeof i= 4 sizeof array= 15 sizeof n= 8 6-9-15 cfy

static Has number of implications: Local static variables initialized only once and retain their value. Guaranteed to be automatically initialized to zero if not otherwise initialized. Global static variable inaccessible outside the file. Can be applied to functions. 6-9-15 cfy

Structures! struct <name> { element1; element2; … } 6-9-15 cfy

Structures example struct class { char name[30]; int number; char instructor[25]; int students[35]; }; 6-9-15 cfy

Structures element dereferencing structure-variable.stucture-member; e.g.: x=class.number; 6-9-15 cfy

Arrays of Structures struct class semester[30]; struct grades { char name[30]; int id; int grades[10]; }g[35]; 6-9-15 cfy

Unions struct class semester[30]; union students { long x; char grades[8]; }g[35]; 6-9-15 cfy

sizeof can be applied to unions and structures Structures can be nested. 6-9-15 cfy

Pointers General form: datatype *ptrname; int x=666, y=555; Int *p; p = &x; y = *p; 6-9-15 cfy

Some cc command line options Compiling multiple C files. Linking multiple objects.

$ cat main. c main(){ func(); } $ cat sub. c func(){} $ cc main $ cat main.c main(){ func(); } $ cat sub.c func(){} $ cc main.c /tmp/ccRFdyU8.o: In function `main': main.c:(.text+0xa): undefined reference to `func' collect2: error: ld returned 1 exit status $ cc sub.c /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/crt1.o: In function `_start': (.text+0x20): undefined reference to `main' $ cc main.c sub.c $ cc -c main.c $ cc -c sub.c $ cc main.o sub.o $ cc main.c sub.o $

$ cat main. c #include "tmp. h" main(){ func(); } $ cc -c main. c main $ cat main.c #include "tmp.h" main(){ func(); } $ cc -c main.c main.c:1:17: fatal error: tmp.h: No such file or directory ^ compilation terminated. $ ls -l /tmp/tmp.h -rw-rw-r--. 1 integration integration 0 Mar 3 09:23 /tmp/tmp.h $ cc -c -I /tmp main.c $

Homework Do exercise 1-19 from the text. Write a program which reads stdin and converts any local case characters to upper case. Redo problem 4 from class 2 as a C program. 6-9-15 cfy

problem 4 Write a C program, sort.c, which sorts a list of command line parameters in ascending order. For example, your command will look something like:  $ sort 7 2 3 9 -1 and type enter. Your program will return: -1 2 3 7 9 6-9-15 cfy