Implementation of string functions such as replace, indexof, and substring in Linux C language)

C language is not as rich as a string operation function as Java. Many useful functions have to be written by themselves. After a day, several common functions have been written, which will be useful in the future.

 

[CPP]View plaincopy

1. # Include <string. h>
2. # Include <stdio. h>
3. /* Replace the str2 string that appears for the first time in the str1 string with str3 */
4. Void replacefirst (char * str1, char * str2, char * str3)
5. {
6. Char str4 [strlen (str1) + 1];
7. Char * P;
8. Strcpy (str4, str1 );
9. If (P = strstr (str1, str2 ))! = NULL)/* P points to the first position of str2 in str1 */
10. {
11. While (str1! = P & str1! = NULL)/* move the str1 pointer to the position of P */
12. {
13. Str1 ++;
14. }
15. Str1 [0] = '\ 0';/* converts the value pointed by str1 pointer to/0 to intercept str1 and discard str2 and subsequent content, only content earlier than str2 is retained */
16. Strcat (str1, str3);/* concatenate str3 after str1 to form a new str1 */
17. Strcat (str1, strstr (str4, str2) + strlen (str2);/* strstr (str4, str2) points to str2 and later content (including str2 ), strstr (str4, str2) + strlen (str2) is to move the Pointer Forward to the strlen (str2) bit, skip str2 */
18. }
19. }
20. /* Replace all str2 in str1 with str3 */
21. Void Replace (char * str1, char * str2, char * str3)
22. {
23. While (strstr (str1, str2 )! = NULL)
24. {
25. Replacefirst (str1, str2, str3 );
26. }
27. }
28. /* In the SRC string, the string starting from subscript start to end-1 (before end) is saved in DEST (subscript starts from 0 )*/
29. Void substring (char * DEST, char * SRC, int start, int end)
30. {
31. Int I = start;
32. If (Start> strlen (SRC) return;
33. If (end> strlen (SRC ))
34. End = strlen (SRC );
35. While (I <End)
36. {
37. Dest [I-start] = SRC [I];
38. I ++;
39. }
40. Dest [I-start] = '\ 0 ';
41. Return;
42. }
43. /* Returns the index character in SRC */
44. Char charat (char * SRC, int index)
45. {
46. Char * P = SRC;
47. Int I = 0;
48. If (index <0 | index> strlen (SRC ))
49. Return 0;
50. While (I <index) I ++;
51. Return P [I];
52. }
53. /* Returns the position of str2 that appears in str1 for the first time (index in the following table).-1 */
54. Int indexof (char * str1, char * str2)
55. {
56. Char * P = str1;
57. Int I = 0;
58. P = strstr (str1, str2 );
59. If (P = NULL)
60. Return-1;
61. Else {
62. While (str1! = P)
63. {
64. Str1 ++;
65. I ++;
66. }
67. }
68. Return I;
69. }
70. /* Returns the position (subscript) of the last occurrence of str2 in str1.-1 */
71. Int lastindexof (char * str1, char * str2)
72. {
73. Char * P = str1;
74. Int I = 0, Len = strlen (str2 );
75. P = strstr (str1, str2 );
76. If (P = NULL) Return-1;
77. While (P! = NULL)
78. {
79. For (; str1! = P; str1 ++) I ++;
80. P = P + Len;
81. P = strstr (p, str2 );
82. }
83. Return I;
84. }
85. /* Delete the white space (space character and horizontal tab) before the first non-white space character on the left of Str )*/
86. Void ltrim (char * Str)
87. {
88. Int I = 0, J, Len = strlen (STR );
89. While (STR [I]! = '\ 0 ')
90. {
91. If (STR [I]! = 32 & STR [I]! = 9) break;/* 32: space, 9: horizontal tab */
92. I ++;
93. }
94. If (I! = 0)
95. For (j = 0; j <= len-I; j ++)
96. {
97. STR [J] = STR [J + I];/* move the subsequent characters forward and add the deleted blank position */
98. }
99. }
100. /* Delete all blank characters (space characters and horizontal tabs) after the last non-blank character of Str )*/
101. Void rtrim (char * Str)
102. {
103. Char * P = STR;
104. Int I = strlen (STR)-1;
105. While (I> = 0)
106. {
107. If (P [I]! = 32 & P [I]! = 9) break;
108. I --;
109. }
110. STR [++ I] = '\ 0 ';
111. }
112. /* Delete the blank characters at both ends of Str */
113. Void trim (char * Str)
114. {
115. Ltrim (STR );
116. Rtrim (STR );
117. }

 

 

Save as mystr. C, and create the header file mystr. h:

 

[CPP]View plaincopy

1. Extern void replacefirst (char * str1, char * str2, char * str3 );
2. Extern void Replace (char * str1, char * str2, char * str3 );
3. Extern void substring (char * DEST, char * SRC, int start, int end );
4. Extern char charat (char * SRC, int index );
5. Extern int indexof (char * str1, char * str2 );
6. Extern int lastindexof (char * str1, char * str2 );
7. Extern void ltrim (char * Str );
8. Extern void rtrim (char * Str );
9. Extern void trim (char * Str );

 

 

Write another test file test. C:

 

[CPP]View plaincopy

1. # Include <string. h>
2. # Include <stdio. h>
3. # Include "mystr. H"
4. Void main ()
5. {
6. Char Buf [20] = "012345126 ";
7. Char buf2 [10];
9. Replacefirst (BUF, "12", "9999 ");
10. Printf ("replacefirst: % s/n", Buf );
11. Strcpy (BUF, "012345126 ");
12. Replace (BUF, "12", "9999 ");
13. Printf ("Replace: % s/n", Buf );
14. Strcpy (BUF, "01234560 ");
15. Substring (buf2, Buf, 2, 5 );
16. Printf ("substring: % s/n", buf2 );
17. Printf ("charat: % C/N", charat (BUF, 4 ));
18. Printf ("indexof: % d/N", indexof (BUF, "234 "));
19. Printf ("lastindexof: % d/N", lastindexof (BUF, "0 "));
20. Strcpy (BUF, "0123 ");
21. Ltrim (BUF );
22. Printf ("ltrim: | % S |/N", Buf );
23. Strcpy (BUF, "0123 ");
24. Rtrim (BUF );
25. Printf ("rtrim: | % S |/N", Buf );
26. Strcpy (BUF, "0123 ");
27. Trim (BUF );
28. Printf ("Trim: | % S |/N", Buf );
29. Strcpy (BUF ,"");
30. Trim (BUF );
31. Printf ("trim2: | % S |/N", Buf );
32. }

 

 

Input in Shell

GCC test. c mystr. C-o Str

./Str

Run.

The result is as follows:

 

Replacefirst: 09999345126

Replace: 0999934599996

Substring: 234

Charat: 4

Indexof: 2

Lastindexof: 7

Ltrim: | 0123 |

Rtrim: | 0123 |

Trim: | 0123 |

Trim2: |