C/C++ - 字符串与字符串函数

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1 C/C++

2 Table of contents

4 char C 2

5 char greeting [50] = " How " " are " " you?"; char greeting [50] = " How are you?"; 3

6 printf ("\" Ready, go!\" exclaimed John."); " Ready, go!" exclaimed John. 4

7 (static storage) 5

8 // quotes.c: # include <stdio.h> int main ( void ) { printf ("%s, %p, %c\n", "We", " are ", *" space farers "); return 0; } 6

9 // quotes.c: # include <stdio.h> int main ( void ) { printf ("%s, %p, %c\n", "We", " are ", *" space farers "); return 0; } We, 0 x100000f81, s 6

10 char s [40] = " Hello world!" 7

11 char s [40] = " Hello world!" char s[] = { H, e, l, l, o,, w, o, r, l, d,!, \0 }; 7

12 1 8

13 char s[] = " Hello world!" 9

14 char s[] = " Hello world!" char * s = " Hello world!" 9

15 char s[] = " Hello world!" char * s = " Hello world!" s 9

16 char heart [] = "I love C!"; char * head = "I love math!"; heart head 10

17 (1) for ( i = 0; i < 6; i ++) putchar ( heart [i]); putchar ( \n ); for ( i = 0; i < 6; i ++) putchar ( head [i]); putchar ( \n ); I I love love 11

18 (2) for ( i = 0; i < 6; i ++) putchar (*( heart + i)); putchar ( \n ); for ( i = 0; i < 6; i ++) putchar (*( head + i)); putchar ( \n ); I I love love 12

19 (3) while (* head!= \0 ) putchar (*( head ++) ); I love math! 13

20 (4) head heart head = heart ; heart = head ; 14

21 (5) heart heart [7] = R ; OR *( heart + 7) = R ; 15

22 (5) heart heart [7] = R ; OR *( heart + 7) = R ; 16

23 const char * fruit [4] = { " Apple ", " Pear ", " Orange ", " Peach " }; 4 fruit char fruit[0] fruit[1]... 17

25 18

26 char * name ; scanf ("%s", name ); name 19

27 char name [81]; C malloc 20

28 C scanf() gets() fgets() 21

29 gets() gets( get string) 22

30 gets() // name1.c # include <stdio.h> # define MAX 81 int main ( void ) { char name [ MAX ]; printf ("Hi, what s your name?\n"); gets ( name ); printf (" Nice name, %s.\n", name ); return 0; } 23

31 gets() Hi, what s your name? warning : this program uses gets (), which is unsafe. Xiaoping Zhang Nice name, Xiaoping Zhang. 24

32 gets() Hi, what s your name? warning : this program uses gets (), which is unsafe. Xiaoping Zhang Nice name, Xiaoping Zhang. gets() gets() 24

33 gets() 1 // name2.c: 2 # include <stdio.h> 3 # define MAX 81 4 int main ( void ) 5 { 6 char name [ MAX ]; 7 char * ptr ; 8 printf ("Hi, what s your name?\n"); 9 ptr = gets ( name ); 10 printf ("%s? Ah! %s!\n", name, ptr ); 11 return 0; 12 } 25

34 gets() Hi, what s your name? warning : this program uses gets (), which is unsafe. Xiaoping Zhang Xiaoping Zhang? Ah! Xiaoping Zhang! 26

35 fgets() gets() fgets() 27

36 fgets() gets() fgets() 1. fgets() n fgets() n-1 2. fgets() gets() 3. fgets() stdin() 28

37 fgets() 1 // name3.c 2 # include <stdio.h> 3 # define MAX 81 4 int main ( void ) 5 { 6 char name [ MAX ]; 7 char * ptr ; 8 printf ("Hi, what s your name?\n"); 9 ptr = fgets (name, MAX, stdin ); 10 printf ("%s? Ah! %s!\n", name, ptr ); 11 return 0; 12 } 29

38 gets() Hi, what s your name? Xiaoping Zhang Xiaoping Zhang? Ah! Xiaoping Zhang! 30

39 gets() Hi, what s your name? Xiaoping Zhang Xiaoping Zhang? Ah! Xiaoping Zhang! fgets fgets 30

40 scanf() %s scanf() scanf() gets() scanf() gets() 31

41 scanf() scanf() 1. %s 2. %10s scanf() 10 32

42 scanf() 1: _ name scanf("%s", name); Fleebert_Hup Fleebert _Hup scanf("%5s", name); Fleebert_Hup Fleeb ert_hup scanf("%5s", name); Ann_Ular Ann _Ular 33

43 scanf() // scan_str.c: # include <stdio.h> int main ( void ) { char name1 [11], name2 [11]; int count ; printf (" Please enter 2 names.\n"); count = scanf ("%5s %10 s",name1, name2 ); printf ("I read the %d names %s and %s.\n", count, name1, name2 ); return 0; } 34

44 scanf() Please enter 2 names. Jesse Jukes I read the 2 names Jesse and Jukes. Please enter 2 names. Liza Applebottham I read the 2 names Liza and Applebotth. Please enter 2 names. Portensia Callowit I read the 2 names Porte and nsia. 35

46 puts() C puts() fputs() printf() 36

47 puts() i // put_out.c: # include <stdio.h> # define DEF "I am a # defined string." int main ( void ) { char str1 [80] = "An array was initialized to me."; const char * str2 = "A pointer was initialized to me."; puts ("I m an argument to puts ()."); puts ( DEF ); puts ( str1 ); puts ( str2 ); puts (& str1 [5]) ; puts ( str2 +4) ; return 0; } 37

48 puts() I m an argument to puts (). I am a # defined string. An array was initialized to me. A pointer was initialized to me. ray was initialized to me. inter was initialized to me. 38

49 puts() puts() printf() puts() puts() 39

50 puts() char str1 [ 80] = " An array was initialized to me. ";... puts (& str1 [5]) ; ray was initialized to me. 40

51 puts() char str1 [ 80] = " An array was initialized to me. ";... puts (& str1 [5]) ; ray was initialized to me. &str1[5] str1 6 r puts() 40

52 puts() const char * str2 = " A pointer was initialized to me.";... puts ( str2 +4) ; inter was initialized to me. 41

53 puts() const char * str2 = " A pointer was initialized to me.";... puts ( str2 +4) ; inter was initialized to me. str2+4 i puts() 41

54 puts() 1 // nono.c: 2 # include <stdio.h> 3 int main ( void ) 4 { 5 char side_a [] = " Side A"; 6 char dont [] = { W, O, W,! }; 7 char side_b [] = " Side B"; 8 9 puts ( dont ); return 0; 12 } 42

55 puts() 1 // nono.c: 2 # include <stdio.h> 3 int main ( void ) 4 { 5 char side_a [] = " Side A"; 6 char dont [] = { W, O, W,! }; 7 char side_b [] = " Side B"; 8 9 puts ( dont ); return 0; 12 } 42

56 puts() WOW! Side A 43

57 puts() WOW! Side A dont puts() dont side_a dont 43

58 fputs() fputs() puts() fputs() stdout stdout stdio.h puts() fputs() 44

59 fputs() gets() puts() char line [81]; while ( gets ( line )) puts ( line ); 45

60 fputs() fgets() fputs() char line [81]; while ( fgets (line, 81, stdin )) fputs (line, stdout ); line 46

61 fputs() puts() gets() fputs() fgets() 47

62 printf() printf() puts() printf ("%s\n", string ); puts ( string ); 48

63 printf() printf() printf ("Well, %s, %s\n", name, MSG ); 49

65 C string.h 1. strlen() 2. strcat() 3. strncat() 4. strcmp() 5. strncmp() 6. strcpy() 7. strncpy() 50

66 strlen() int * strlen ( const char * s); s s 51

67 strlen() i // test_fit.c # include <stdio.h> # include <string.h> void fit ( char *, unsigned int ); int main ( void ) { char mesg [] = " Hold on to your hats, hackers."; puts ( mesg ); fit (mesg,7) ; puts ( mesg ); puts (" Let s look at some more of the string."); puts ( mesg + 8); } return 0; 52

68 strlen() ii void fit ( char * string, unsigned int size ) { if ( strlen ( string ) > size ) *( string + size ) = \0 ; } 53

69 strlen() Hold on to your hats, hackers. Hold on Let s look at some more of the string. to your hats, hackers. 54

70 strcat() char * strcat ( char * s1, const char * s2); s2 s1 s2 s1 55

71 strcmp() s1 s2 strcat() char * s1 56

72 strcat() i # include <stdio.h> # include <string.h> # define SIZE 80 int main ( void ) { char flower [ SIZE ]; char addon [] = " s smell like old shoes."; puts (" What is your favorite flower?"); gets ( flower ); strcat ( flower, addon ); puts ( flower ); puts ( addon ); } return 0; 57

73 strcat() ii 58

74 strcat() What is your favorite flower? Rose Roses smell like old shoes. s smell like old shoes. 59

75 strncat() strcat() strncat() 60

76 strncat() char * strcat ( char * s1, const char * s2, size_t n); s2 n s1 s2 s1 strncat() char * s1 61

77 strncat() i # include <stdio.h> # include <string.h> # define SIZE 30 # define BUGSIZE 4 int main ( void ) { char flower [ SIZE ]; char addon [] = " s smell like old shoes."; char bug [ BUGSIZE ]; int available ; puts (" What is your favorite flower?"); gets ( flower ); if (( strlen ( addon ) + strlen ( flower ) + 1) <= SIZE ) strcat ( flower, addon ); puts ( flower ); 62

78 strncat() ii puts (" What is your favorite bug?"); gets ( bug ); available = BUGSIZE - strlen ( bug ) - 1; strncat (bug, "is sdfsdf ", 1); puts ( bug ); } return 0; 63

79 strncat() What is your favorite flower? Rose Roses smell like old shoes. What is your favorite bug? Aphid Aphids smell 64

80 strcmp() int strcmp ( const char * s1, const char * s2); s1 s2 0 ASCII 65

81 strcmp() 66

82 strcmp() i /* compare. c -- this will work */ # include <stdio.h> # include <string.h> # define ANSWER " Grant " # define MAX 40 int main ( void ) { char try [ MAX ]; puts (" Who is buried in Grant s tomb?"); gets ( try ); while ( strcmp (try, ANSWER )!= 0) { puts ("No, that s wrong. Try again."); gets ( try ); } puts (" That s right!"); 67

83 strcmp() ii } return 0; 68

84 strcmp() strcmp ("A", "A") is 0 strcmp ("A", "B") is -1 strcmp ("B", "A") is 1 strcmp ("C", "A") is 2 strcmp ("Z", "a") is -7 strcmp (" apples ", " apple ") is

85 strcmp() strcmp ("A", "A") is 0 strcmp ("A", "B") is -1 strcmp ("B", "A") is 1 strcmp ("C", "A") is 1 strcmp ("Z", "a") is -1 strcmp (" apples ", " apple ") is 1 70

86 strncmp() int strncmp ( const char * s1, const char * s2, size_t n); s1 s2 n strcmp() 71

87 strncmp() "astro" 5 72

88 strncmp() i /* starsrch.c -- use strncmp () */ # include <stdio.h> # include <string.h> # define LISTSIZE 5 int main ( void ) { const char * list [ LISTSIZE ] = { " astronomy ", " astounding ", " astrophysics ", " ostracize ", " asterism " }; int count = 0; int i; for ( i = 0; i < LISTSIZE ; i ++) if ( strncmp ( list [i]," astro ", 5) == 0) 73

89 strncmp() ii { printf (" Found : %s\n", list [i]); count ++; } printf (" The list contained % d words beginning " " with astro.\n", count ); } return 0; 74

90 strncmp() Found : astronomy Found : astrophysics The list contained 2 words beginning with astro. 75

91 strcpy() char * strcpy ( char * s1, const char * s2); s2 s1 s1 76

92 strcpy() s2 (source) s1 (target) s2 s1 s2 77

93 strcpy() i /* copy1.c -- strcpy () demo */ # include <stdio.h> # include <string.h> # define SIZE 40 # define LIM 5 int main ( void ) { char qwords [ LIM ][ SIZE ]; char temp [ SIZE ]; int i = 0; printf (" Enter %d words beginning with q:\n", LIM ); while (i < LIM && gets ( temp )) { if ( temp [0]!= q ) printf ("%s doesn t begin with q!\n", temp ); 78

94 strcpy() ii } else { strcpy ( qwords [i], temp ); i ++; } } puts (" Here are the words accepted :"); for ( i = 0; i < LIM ; i ++) puts ( qwords [i]); return 0; 79

95 strcpy() Enter 5 words beginning with q: quit quarter quite quotient nomore nomore doesn t begin with q! quiz Here are the words accepted : quit quarter quite quotient quiz 80

96 strcpy() strcpy() char * 81

97 strcpy() # include <stdio.h> # include <string.h> # define WORDS " beast " # define SIZE 40 int main ( void ) { const char * orig = WORDS ; char copy [ SIZE ] = " Be the best that you can be."; char * ps; puts ( orig ); puts ( copy ); ps = strcpy ( copy + 7, orig ); puts ( copy ); puts (ps +6) ; return 0; } 82

98 strcpy() beast Be the best that you can be. Be the beast beast 83

99 strncpy() char * strcpy ( char * s1, const char * s2, size_t n); s2 n s1 n 84

100 strncpy() n n n 1 s1 85

101 strncpy() i # include <stdio.h> # include <string.h> # define SIZE 40 # define TARGSIZE 7 # define LIM 5 int main ( void ) { char qwords [ LIM ][ TARGSIZE ]; char temp [ SIZE ]; int i = 0; printf (" Enter %d words begin with q:\n", LIM ); while (i < LIM && gets ( temp )) { if ( temp [0]!= q ) printf ("%s doesn t begin with q!\n", temp ); 86

102 strncpy() ii } else { strncpy ( qwords [i], temp, TARGSIZE - 1); qwords [i][ TARGSIZE - 1] = \0 ; i ++; } } puts (" Here are the words accepted :"); for ( i = 0; i < LIM ; i ++) puts ( qwords [i]); return 0; 87

103 strncpy() Enter 5 words begin with q: quack quadratic quisling quota quagga Here are the words accepted : quack quadra quisli quota quagga 88

104 sprintf() sprintf() stdio.h printf() printf() 89

105 sprintf() i # include <stdio.h> # define MAX 20 int main ( void ) { char first [ MAX ]; char last [ MAX ]; char formal [2* MAX +10]; double prize ; puts (" Enter your first name :"); gets ( first ); puts (" Enter your last name :"); gets ( last ); puts (" Enter your prize money :"); 90

106 sprintf() ii scanf ("%lf", & prize ); sprintf ( formal, "%s, % -19s: $ %6.2 f\n", last, first, prize ); puts ( formal ); } return 0; 91

107 sprintf() Enter your first name : warning : this program uses gets (), which is unsafe. Teddy Enter your last name : Bear Enter your prize money : 2000 Bear, Teddy : $

108 sprintf() Enter your first name : warning : this program uses gets (), which is unsafe. Teddy Enter your last name : Bear Enter your prize money : 2000 Bear, Teddy : $ sprintf() format 92

C/C++程序设计 - 字符串与格式化输入/输出

C/C++程序设计 - 字符串与格式化输入/输出 C/C++ / Table of contents 1. 2. 3. 4. 1 i # include # include // density of human body : 1. 04 e3 kg / m ^3 # define DENSITY 1. 04 e3 int main ( void ) { float weight, volume ; int