C語言string.h中常用字元函式介紹
阿新 • • 發佈：2019-01-07
strcpy
函式名: strcpy
功 能: 拷貝一個字串到另一個
用 法: char
*strcpy(char
*destin, char
*source);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
string[10];
char
*str1 = "abcdefghi";
strcpy(string, str1);
printf("%s\n", string);
return
0;
}
|
strncpy
函式名:strncpy
原型：char* strncpy(char
*dest, char
*src, size_t
n);
功能：將字串src中最多n個字元複製到字元陣列dest中(它並不像strcpy一樣遇到NULL才停止複製，而是等湊夠n個字元才開始複製），返回指向dest的指標。
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
string[10];
char
*str1 = "abcdefghi";
strncpy(string, str1,3);
printf("%s\n", string);
return0;
}
|
strcat
函式名: strcat
功 能: 字串拼接函式
用 法: char
*strcat(char
*destin, char
*source);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
destination[25];
char
*blank = " ", *c =
"C++", *Borland =
"Borland";
strcpy(destination, Borland);
strcat(destination, blank);strcat(destination, c);
printf("%s\n", destination);
return
0;
}
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strchr
函式名: strchr
功 能: 在一個串中查詢給定字元的第一個匹配之處\
用 法: char
*strchr(char
*str, char
c);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
string[15];
char
*ptr, c = 'r';
strcpy(string,
"This is a string");
ptr = strchr(string, c);
if
(ptr)
printf("The character %c is at position: %d\n", c, ptr-string);
else
printf("The character was not found\n");
return
0;
}
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strcmp
函式名: strcmp
功 能: 串比較
用 法: int
strcmp(char
*str1, char
*str2);
看Asic碼，str1>str2，返回值 > 0；兩串相等，返回0
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*buf1 = "aaa", *buf2 =
"bbb", *buf3 =
"ccc";
int
ptr;
ptr = strcmp(buf2, buf1);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 1\n");
else
printf("buffer 2 is less than buffer 1\n");
ptr = strcmp(buf2, buf3);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 3\n");
else
printf("buffer 2 is less than buffer 3\n");
return
0;
}
|
strnicmp
函式名: strnicmp
功 能: 將一個串中的一部分與另一個串比較, 不管大小寫
用 法: int
strnicmp(char
*str1, char
*str2, unsigned maxlen);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*buf1 = "BBB", *buf2 =
"bbb";
int
ptr;
ptr = strnicmp(buf2, buf1);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 1\n");
if
(ptr < 0)
printf("buffer 2 is less than buffer 1\n");
if
(ptr == 0)
printf("buffer 2 equals buffer 1\n");
return
0;
}
|
strlen
函式名:strlen
功能: strlen函式求的是字串的長度，它求得方法是從字串的首地址開始到遇到第一個'\0'停止計數,如果你只定義沒有給它賦初值，這個結果是不定的，它會從字串首地址一直記下去，直到遇到'\0'才會停止。
原型: size_t
strlen(const
char *s);
#include<stdio.h>
#include <string.h>
int
main()
{ int
i=0;
char
*he ="Hello,world";
i=strlen(he);
printf("字串長度為%d\n",i);
return
0;
} //
執行結果：
字串長度為11
|
strcspn
函式名: strcspn
功 能: 在串中查詢第一個給定字符集內容的段
用 法: int
strcspn(char
*str1, char
*str2);
程式例:
#include <stdio.h>
#include <string.h>
#include <alloc.h>
int
main(void)
{
char
*string1 = "1234567890";
char
*string2 = "747DC8";
int
length;
length = strcspn(string1, string2);
printf("Character where strings intersect is at position %d\n", length);
return
0;
}
|
strdup
函式名: strdup
功 能: 將串拷貝到新建的位置處
用 法: char
*strdup(char
*str);
程式例:
#include <stdio.h>
#include <string.h>
#include <alloc.h>
int
main(void)
{
char
*dup_str, *string = "abcde";
dup_str = strdup(string);
printf("%s\n", dup_str);
free(dup_str);
return
0;
}
|
stricmp
函式名:stricmp
功 能: 以大小寫不敏感方式比較兩個串
用 法: int
stricmp(char
*str1, char *str2);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*buf1 = "BBB", *buf2 =
"bbb";
int
ptr;
ptr = stricmp(buf2, buf1);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 1\n");
if
(ptr < 0)
printf("buffer 2 is less than buffer 1\n");
if
(ptr == 0)
printf("buffer 2 equals buffer 1\n");
return
0;
}
|
strerror
函式名: strerror
功 能: 返回指向錯誤資訊字串的指標
用 法: char
*strerror(int
errnum);
程式例:
#include <stdio.h>
#include <errno.h>
int
main(void)
{
char
*buffer;
buffer = strerror(errno);
printf("Error: %s\n", buffer);
return
0;
}
|
strcmpi
函式名: strcmpi
功 能: 將一個串與另一個比較, 不管大小寫
用 法: int
strcmpi(char
*str1, char *str2);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*buf1 = "BBB", *buf2 =
"bbb";
int
ptr;
ptr = strcmpi(buf2, buf1);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 1\n");
if
(ptr < 0)
printf("buffer 2 is less than buffer 1\n");
if
(ptr == 0)
printf("buffer 2 equals buffer 1\n");
return
0;
}
|
strnicmp
函式名: strnicmp
功 能: 不注重大小寫地比較兩個串
用 法: int
strnicmp(char
*str1, char
*str2, unsigned maxlen);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*buf1 = "BBBccc", *buf2 =
"bbbccc";
int
ptr;
ptr = strnicmp(buf2, buf1, 3);
if
(ptr > 0)
printf("buffer 2 is greater than buffer 1\n");
if
(ptr < 0)
printf("buffer 2 is less than buffer 1\n");
if
(ptr == 0)
printf("buffer 2 equals buffer 1\n");
return
0;
}
|
strnset
函式名: strnset
功 能: 將一個字串前n個字元都設為指定字元
用 法: char
*strnset(char
*str, char
ch, unsigned n);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
*string = "abcdefghijklmnopqrstuvwxyz";
char
letter = 'x';
printf("string before strnset: %s\n", string);
strnset(string, letter, 13);
printf("string after strnset: %s\n", string);
return
0;
}
|
strpbrk
函式名: strpbrk
功 能: 在串中查詢給定字符集中的字元
用 法: char
*strpbrk(char
*str1, char
*str2);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
*string1 = "abcdefghijklmnopqrstuvwxyz";
char
*string2 = "onm";
char
*ptr;
ptr = strpbrk(string1, string2);
if
(ptr)
printf("strpbrk found first character: %c\n", *ptr);
else
printf("strpbrk didn't find character in set\n");
return
0;
}
|
strrchr
函式名: strrchr
功 能: 在串中查詢指定字元的最後一個出現
用 法: char
*strrchr(char
*str, char
c);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
string[15];
char
*ptr, c = 'r';
strcpy(string,
"This is a string");
ptr = strrchr(string, c);
if
(ptr)
printf("The character %c is at position: %d\n", c, ptr-string);
else
printf("The character was not found\n");
return
0;
}
|
strrev
函式名: strrev
功 能: 串倒轉
用 法: char
*strrev(char
*str);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
*forward = "string";
printf("Before strrev(): %s\n", forward);
strrev(forward);
printf("After strrev(): %s\n", forward);
return
0;
}
|
strset
函式名: strset
功 能: 將一個串中的所有字元都設為指定字元
用 法: char
*strset(char
*str, char c);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
string[10] = "123456789";
char
symbol = 'c';
printf("Before strset(): %s\n", string);
strset(string, symbol);
printf("After strset(): %s\n", string);
return
0;
}
|
strstr
函式名: strstr
功 能: 在串中查詢指定字串的第一次出現
用 法: char
*strstr(char
*str1, char
*str2);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
*str1 = "Borland International", *str2 =
"nation", *ptr;
ptr = strstr(str1, str2);
printf("The substring is: %s\n", ptr);
return
0;
}
|
strtod
函式名: strtod
功 能: 將字串轉換為double型值
用 法: double
strtod(char
*str, char
**endptr);
程式例:
#include <stdio.h>
#include <stdlib.h>
int
main(void)
{
char
input[80], *endptr;
double
value;
printf("Enter a floating point number:");
gets(input);
value = strtod(input, &endptr);
printf("The string is %s the number is %lf\n", input, value);
return
0;
}
|
strtok
函式名: strtok
功 能: 查詢由在第二個串中指定的分界符分隔開的單詞
用 法: char
*strtok(char
*str1, char
*str2);
程式例:
#include <string.h>
#include <stdio.h>
int
main(void)
{
char
input[16] = "abc,d";
char
*p;
/* strtok places a NULL terminator
in front of the token, if found */
p = strtok(input,
",");
if
(p) printf("%s\n", p);
/* A second call to strtok using a NULL
as the first parameter returns a pointer
to the character following the token */
p = strtok(NULL,
",");
if
(p) printf("%s\n", p);
return
0;
}
|
strtol
函式名: strtol
功 能: 將串轉換為長整數
用 法: long
strtol(char
*str, char
**endptr, int
base);
程式例:
#include <stdlib.h>
#include <stdio.h>
int
main(void)
{
char
*string = "87654321", *endptr;
long
lnumber;
/* strtol converts string to long integer */
lnumber =
strtol(string, &endptr, 10);
printf("string = %s long = %ld\n", string, lnumber);
return
0;
}
|
strupr
函式名:strupr
功 能: 將串中的小寫字母轉換為大寫字母
用 法: char
*strupr(char
*str);
程式例:
#include <stdio.h>
#include <string.h>
int
main(void)
{
char
string[ ] = "abcdefghijklmnopqrstuvwxyz", *ptr;//定義為陣列才能修改
/* converts string to upper case chara
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