你们要的C语言实例大全-深入提高篇二

目录

实例56　fputc()和fgetc()

实例57　函数rewind()

实例58　fread()和fwrite()

实例59　fprintf()和fscanf()

实例60　随机存取

实例61　错误处理

实例62　综合实例

实例63　动态分配函数

实例64　常用时间函数

’实例65　转换函数

实例66　查找函数

实例67　跳转函数

实例68　排序函数

实例69　伪随机数生成

实例70　可变数目变元

---

实例56　fputc()和fgetc()

convert.c

# include <stdio.h>
# include <string.h>
# include <stdlib.h>

void main()
{
	FILE *fp;
	char str[100];
	int i;

	if((fp=fopen("file.txt", "w"))==NULL)
	{
		printf("无法打开文件\n");
		exit(0);
	}

	printf("请输入一个字符串：\n");
	gets(str);

	/* 将字符串中的小写字符转换成大写字符，直到遇到"."为止 */
	for(i=0; str[i]!='.'; i++)
	{
		if(str[i]>='a' && str[i]<='z')
			str[i] = str[i] - 32;
		fputc(str[i], fp);  /* 将转换后的字符存入文件 */
	}
	fclose(fp);

	fp = fopen("file.txt", "r");
	for(i=0; str[i]!='.'; i++)
		str[i] = fgetc(fp);
	printf("%s\n", str);
	fclose(fp);
}

 

运行

[email protected]:~/test/clanguage$ ./a.out 
请输入一个字符串：
shilasgjtg.
SHILASGJTG.

实例57　函数rewind()

rewind.c

# include <stdio.h>
# include <stdlib.h>
# include <string.h>

void main()
{
	char str[80];
	FILE *fp;  /* 定义一个文件类型的指针 */

	/* 以写的方式打开文件test */
	if((fp=fopen("test.txt", "w"))==NULL)
	{
		printf("Cannot open file.\n");
		exit(0);
	}

	do{
		printf("Please enter a string: \n");
		gets(str);
		strcat(str, "\n");  /* 增加一个新行 */
		fputs(str, fp);
	} while(*str!='\n');

	/* 从文件中读出字符串,并将它们显示出来 */
	rewind(fp);  /* 重置文件指针 */
	while(!feof(fp))
	{
		fgets(str, 79, fp);
		printf(str);
	}

	fclose(fp);
}

运行

[email protected]:~/test/clanguage$ cat test.txt 
lashdidsagh
idhsig
hjiheiw
asg

实例58　fread()和fwrite()

fread.c

# include <stdio.h>
# include <stdlib.h>

void main()
{
	FILE *fp;
	int i = 156;
	long l = 9701076L;
	double d = 3.456;

	if((fp=fopen("test", "w"))==NULL)
	{
		printf("不能打开文件.\n");
		exit(0);
	}

	fwrite(&i, sizeof(int), 1, fp);
	fwrite(&l, sizeof(long), 1, fp);
	fwrite(&d, sizeof(double), 1, fp);

	rewind(fp);

	fread(&i, sizeof(int), 1, fp);
	fread(&l, sizeof(long), 1, fp);
	fread(&d, sizeof(double), 1, fp);

	printf("i = %d\n", i);
	printf("l = %ld\n", l);
	printf("d = %f\n", d);

	fclose(fp);
}

运行

[email protected]:~/test/clanguage$ ./a.out 
i = 156
l = 9701076
d = 3.456000

实例59　fprintf()和fscanf()

fprintf.c

# include <stdio.h>
# include <io.h>
# include <stdlib.h>

void main()
{
	FILE *fp;
	char str[80];
	int i;

	if((fp=fopen("test", "w"))==NULL)
	{
		printf("不能打开文件.\n");
		exit(0);
	}

	printf("Please enter a string and a number: \n");
	fscanf(stdin, "%s %d", str, &i);  /* 参数stdin表示从键盘读入 */
	fprintf(fp, "%s %d", str, i);
	fclose(fp);

	if((fp=fopen("test", "r"))==NULL)
	{
		printf("不能打开文件.\n");
		exit(0);
	}

	fscanf(fp, "%s %d", str, &i);
	fprintf(stdout, "%s %d\n", str, i);  /* 参数stdout表示写向屏幕 */
	fclose(fp);
}

运行

[email protected]:~/test/clanguage$ ./a.out 
Please enter a string and a number: 
sahig 12
sahig 12
[email protected]:~/test/clanguage$ cat test
sahig [email protected]:~/test/clanguage$ 

实例60　随机存取

fseek.c

# include <stdio.h>
# include <stdlib.h>

void main(int argc, char *argv[])
{
	FILE *fp;

	if(argc!=3)
	{
		printf("缺少字节位置，无法进行操作。\n");
		exit(0);
	}

	if((fp=fopen(argv[1], "rb"))==NULL)
	{
		printf("无法打开文件。\n");
		exit(0);
	}

	if(fseek(fp, atol(argv[2]), 0))
	{
		printf("寻找出现错误。\n");
		exit(0);
	}

	printf("在%ld处的字符是%c。\n", atol(argv[2]), getc(fp));
	fclose(fp);
}

运行

[email protected]:~/test/clanguage$ ./a.out test 2
在2处的字符是h。

实例61　错误处理

ferror.c

# include <stdio.h>
# include <stdlib.h>

# define TAB_NUM 8    /* 定义应换的空格数 */
# define IN 0
# define OUT 1

void error(int e)
{
	if(e == IN)
		printf("输入错误。\n");
	else
		printf("输出错误。\n");
	exit(1);    /* 跳出程序 */
}

/* 为使用该程序，应该指定命令行中的输入和输出出文件名 */
void main(int argc, char *argv[])   
{
	FILE *in, *out;
	int tab, i;
	char ch;

	if(argc != 3)
	{
		printf("用法出错。\n");
		exit(1);
	}

	if((out=fopen(argv[1], "wb"))==NULL)
	{
		printf("不能打开输入文件%s。\n", argv[1]);
		exit(1);
	}

	if((out=fopen(argv[2], "wb"))==NULL)
	{
		printf("不能打开输出文件%s。\n", argv[2]);
		exit(1);
	}

	tab = 0;
	do{
		ch = getc(in);
		if(ferror(in))
			error(IN);

		/* 如果发现制表符，则输出相同数目的空格符 */
		if(ch == '\t')
		{
			for(i=tab; i<8; i++)
			{
				putc(' ', out);
				if(ferror(out))
					error(OUT);
			}
			tab = 0;
		}
		else
		{
			putc(ch, out);
			if(ferror(out))
				error(OUT);
			tab++;
			if(tab==TAB_NUM)
				tab = 0;
			if(ch=='\n'||ch=='\r')
				tab = 0;
		}
	} while(!feof(in));

	fclose(in);
	fclose(out);
}

实例62　综合实例

commu.c

# include <stdio.h>
# include <stdlib.h>

# define MAX 100

struct addr
{
	char name[20];
	char street[40];
	char city[20];
	char state[4];
	unsigned long zip;
} addr_list[MAX];

void init_list(void);
void enter(void);
void dele(void);
void list(void);
void save(void);
void load(void);
int menu_select(void);
int find_free(void);

void main()
{
	char choice;

	init_list();
	for( ; ; )
	{
		choice = menu_select();
		switch(choice)
		{
		case 1: enter();
			    break;
		case 2: dele();
			    break;
		case 3: list();
			    break;
		case 4: save();
				break;
		case 5: load();
				break;
		case 6: exit(0);
		}
	}
}

void init_list(void)
{
	register int t;

	for(t=0; t<MAX; t++)
		addr_list[t].name[0] = '\0';
}

void enter(void)
{
	int slot;
	char str[80];
	
	slot = find_free();

	if(slot == -1)
		printf("\nList Full");

	printf("Enter name: ");
	gets(addr_list[slot].name);

	printf("Enter street: ");
	gets(addr_list[slot].street);

	printf("Enter city: ");
	gets(addr_list[slot].city);

	printf("Enter state: ");
	gets(addr_list[slot].state);

	printf("Enter zip: ");
	gets(str);
	addr_list[slot].zip = strtoul(str, '\0', 10);
}

void dele(void)
{
	register int slot;
	char str[80];

	printf("Enter record #: ");
	gets(str);
	slot = atoi(str);

	if(slot>=0 && slot<MAX)
		addr_list[slot].name[0] = '\0';
}

void list(void)
{
	register int t;

	for(t=0; t<MAX; t++)
	{
		if(addr_list[t].name[0])
		{
			printf("%s\n", addr_list[t].name);
			printf("%s\n", addr_list[t].street);
			printf("%s\n", addr_list[t].city);
			printf("%s\n", addr_list[t].state);
			printf("%s\n\n", addr_list[t].zip);
		}
	}
	printf("\n\n");
}

void save(void)
{
	FILE *fp;
	register int i;

	if((fp=fopen("maillist", "wb"))==NULL)
		printf("Cannot open file.\n");

	for(i=0; i<MAX; i++)
		if(*addr_list[i].name)
			if(fwrite(&addr_list[i], sizeof(struct addr), 1, fp)!=1)
				printf("File write error.\n");

	fclose(fp);
}

void load(void)
{
	FILE *fp;
	register int i;

	if((fp=fopen("maillist", "rb"))==NULL)
		printf("Cannot open file.\n");

    init_list();
	for(i=0; i<MAX; i++)
		if(fread(&addr_list[i], sizeof(struct addr), 1, fp)!=1)
		{
			if(feof(fp))
				break;
			printf("File read error.\n");
		}

	fclose(fp);
}

int menu_select(void)
{
	char str[80];
	int c;

	printf("1. Enter a name\n");
	printf("2. Delete a name\n");
	printf("3. List the file\n");
	printf("4. Save the file\n");
	printf("5. Load the file\n");
	printf("6. Quit\n");

	do{
		printf("\nEnter your choice: ");
		gets(str);
		c = atoi(str);
	} while(c<0 || c>6);
	
	return c;
}

int find_free(void)
{
	register int t;

	for(t=0; addr_list[t].name[0]&&t<MAX; t++);

	if(t==MAX) 
		return -1;

	return t;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
1. Enter a name
2. Delete a name
3. List the file
4. Save the file
5. Load the file
6. Quit

Enter your choice: 1
Enter name: gll   
Enter street: s
Enter city: china
Enter state: sx
Enter zip: z
1. Enter a name
2. Delete a name
3. List the file
4. Save the file
5. Load the file
6. Quit

Enter your choice: 6 

实例63　动态分配函数

dynamic.c

# include <stdio.h>
# include <stdlib.h>

# define NUM 10

int main()
{
	char *str[NUM];  /* 定义一个字符性的指针数组 */
	int t;

	/* 为数组中的每个指针分配内存 */
	for(t=0; t<NUM; t++)
	{
		if((str[t]=(char *)malloc(128))==NULL)
		{
			printf("Allocation Error.\n");
			exit(1);
		}
		/* 在分配的内存中存放字符串 */
		printf("Enter string %d: ", t);
		gets(str[t]);
	}
	
	/* 释放内存 */
	for(t=0; t<NUM; t++)
		free(str[t]);

	/* 由于主函数有返回值，故返回0值 */
	return 0;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
Enter string 0: s
Enter string 1: f
Enter string 2: g
Enter string 3: y
Enter string 4: h
Enter string 5: r
Enter string 6: h
Enter string 7: c
Enter string 8: a
Enter string 9: x

实例64　常用时间函数

time.c

# include <time.h>
# include <stdio.h>

int main()
{
	struct tm *local;
	time_t tm;

	tm = time(NULL);
	local = localtime(&tm);
	printf("Local time and date: %s\n", asctime(local));

	local = gmtime(&tm);
	printf("UTC time and date: %s\n", asctime(local));

	return 0;
}

运行‘

[email protected]:~/test/clanguage$ ./a.out 
Local time and date: Sun Mar  8 08:44:08 2020

UTC time and date: Sun Mar  8 15:44:08 2020

’
实例65　转换函数

convert.c

# include <stdlib.h>
# include <stdio.h>

int main()
{
	char num1[80], num2[80];
	double sum1;
	int sum2;
	long sum3;

	printf("Enter first: ");
	gets(num1);
	printf("Enter second: ");
	gets(num2);
	sum1 = atof(num1)+atof(num2);
	printf("The sum is: %f\n", sum1);

	printf("Enter three: ");
	gets(num1);
	printf("Enter four: ");
	gets(num2);
	sum2 = atoi(num1)+atoi(num2);
	printf("The sum is: %d\n", sum2);

	printf("Enter five: ");
	gets(num1);
	printf("Enter six: ");
	gets(num2);
	sum3 = atol(num1)+atol(num2);
	printf("The sum is: %ld\n", sum3);

	return 0;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
Enter first: 12
Enter second: 45
The sum is: 57.000000
Enter three: 77
Enter four: 98
The sum is: 175
Enter five: 90
Enter six: 111
The sum is: 201

实例66　查找函数

search.c

# include <stdio.h>
# include <stdlib.h>
# include <ctype.h>

char *alpha = "abcdefghijklmnopqrstuvwxyz";

int comp(const void *ch, const void *s);

int main()
{
	char ch;
	char *p;

	printf("Enter a character: ");
	ch = getchar();
	ch = tolower(ch);    /* 将变元ch转换成小写字符 */
	p = (char *)bsearch(&ch, alpha, 26, 1, comp);
	if(p)
		printf("%c is in alphabet\n", *p);
	else
		printf("is not in alphabet\n");

	return 0;
}

int comp(const void *ch, const void *s)
{
	return *(char *)ch -*(char *)s;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
Enter a character: i
i is in alphabet

实例67　跳转函数

jump.c

# include <setjmp.h>
# include <stdio.h>

jmp_buf ebuf;    /* 类型在<setjmp.h>中定义 */
void fun(void);

int main()
{
	int i;

	printf("1 ");
	i = setjmp(ebuf);    /* 第一次调用时返回值为零 */
	if(i == 0)
	{
		fun();
		printf("This will not be printed.");
	}
	printf("%d\n", i);

	return 0;
}

void fun(void)
{
	printf("3 ");
	longjmp(ebuf, 5);    /* 跳转到执行setjmp()的地方，但此时函数setjmp()返回值为3 */
}

运行

[email protected]:~/test/clanguage$ ./a.out 
1 3 5

实例68　排序函数

sort.c

# include <stdlib.h>
# include <stdio.h>

int num[12] = {
	14, 5, 9, 7, 6, 0, 91, 4, 1, 3, 2, 8
};

int comp(const void *, const void *);

int main()
{
	int i;

	printf("Original array: ");
	for(i=0; i<12; i++)
		printf("%d ", num[i]);
	printf("\n");

	qsort(num, 12, sizeof(int), comp);

	printf("Sorted array: ");
	for(i=0; i<12; i++)
		printf("%d ", num[i]);
	printf("\n");

	return 0;
}

int comp(const void *i, const void *j)
{
	return *(int *)i - *(int *)j;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
Original array: 14 5 9 7 6 0 91 4 1 3 2 8 
Sorted array: 0 1 2 3 4 5 6 7 8 9 14 91 

实例69　伪随机数生成

rand.c

# include <stdio.h>
# include <stdlib.h>
# include <time.h>

/* 利用系统时间来寻找随机数，并将前十个随机数显示出来 */
int main()
{
	long time1;
	int i, time2;

	/* 获得正确的日历时间 */
	time1 = time(NULL);    /* 返回系统的当前日历时间 */
	printf("%ld\n", time1);

	time2 = (unsigned)time1/2;
	printf("%ld\n", time2);

	/* 以系统时间为参数，为即将生成的伪随机数序列设置起点 */
	srand(time2);

	/* 生成十个伪随机数序列 */
	for(i=0; i<10; i++)
		printf("%d ", rand());
	printf("\n");

	return 0;
}

运行

[email protected]:~/test/clanguage$ ./a.out 
1583682555
791841277
937882791 822067410 1112968171 837771753 1392239192 870112025 1562303515 1412078305 1705961954 752498124 

实例70　可变数目变元

change.c

# include <stdio.h>
# include <stdarg.h>

double sum_series(int num, ...);

int main()
{
	double d;

	d = sum_series(4, 0.5, 0.25, 0.125, 0.0625);

	printf("Sum of series is %f.\n", d);

	return 0;
}

double sum_series(int num, ...)
{
	double sum = 0.0, t;
	va_list argptr;

	/* 初始化argptr */
	va_start(argptr, num);

	/* 计算序列之和 */
	for( ; num; num--)
	{
		t = va_arg(argptr, double);
		sum = sum + t;
	}

	va_end(argptr);
	return sum;
}

运行

trust1[email protected]:~/test/clanguage$ ./a.out 
Sum of series is 0.937500.