C语言库函数(S类字母)

2019-11-17 05:43:06

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函数名: sound
功  能: 以指定频率打开PC扬声器
用  法: void sound(unsigned frequency);
程序例:

/* Emits a 7-Hz tone for 10 seconds.
   Your PC may not be able to emit a 7-Hz tone. */
#include <dos.h>

int main(void)
{
   sound(7);
   delay(10000);
   nosound();
   return 0;
}




函数名: spawnl
功  能: 创建并运行子程序
用  法: int spawnl(int mode, char *pathname, char *arg0,
     arg1, ... argn, NULL);
程序例:

#include <PRocess.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
   int result;

   clrscr();
   result = spawnl(P_WAIT, "tcc.exe", NULL);
   if (result == -1)
   {
      perror("Error from spawnl");
      exit(1);
   }
   return 0;
}



函数名: spawnle
功  能: 创建并运行子程序
用  法: int spawnle(int mode, char *pathname, char *arg0,
      arg1,..., argn, NULL);
程序例:

/* spawnle() example */

#include <process.h>
#include <stdio.h>
#include <conio.h>

int main(void)
{
   int result;

   clrscr();
   result = spawnle(P_WAIT, "tcc.exe", NULL, NULL);
   if (result == -1)
   {
      perror("Error from spawnle");
      exit(1);
   }
   return 0;
}




函数名: sprintf
功  能: 送格式化输出到字符串中

用  法: int sprintf(char *string, char *farmat [,argument,...]);
程序例:

#include <stdio.h>
#include <math.h>

int main(void)
{
   char buffer[80];

   sprintf(buffer, "An approximation of Pi is %f/n", M_PI);
   puts(buffer);
   return 0;
}



函数名: sqrt
功  能: 计算平方根
用  法: double sqrt(double x);
程序例:

#include <math.h>
#include <stdio.h>

int main(void)
{
    double x = 4.0, result;

    result = sqrt(x);
    printf("The square root of %lf is %lf/n", x, result);
    return 0;
}


函数名: srand
功  能: 初始化随机数发生器
用  法: void srand(unsigned seed);
程序例:

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

int main(void)
{
   int i;
   time_t t;

   srand((unsigned) time(&t));
   printf("Ten random numbers from 0 to 99/n/n");
   for(i=0; i<10; i++)
       printf("%d/n", rand() % 100);
   return 0;
}



函数名: sscanf
功  能: 执行从字符串中的格式化输入
用  法: int sscanf(char *string, char *format[,argument,...]);
程序例:

#include <stdio.h>
#include <conio.h>

int main(void)
{
   char label[20];
   char name[20];
   int entries = 0;
   int loop, age;
   double salary;

   strUCt Entry_struct

   {
      char  name[20];
      int   age;
      float salary;
   } entry[20];

/* Input a label as a string of characters restricting to 20 characters */
   printf("/n/nPlease enter a label for the chart: ");
   scanf("%20s", label);
   fflush(stdin);  /* flush the input stream in case of bad input */

/* Input number of entries as an integer */
   printf("How many entries will there be? (less than 20) ");
   scanf("%d", &entries);
   fflush(stdin);   /* flush the input stream in case of bad input */

/* input a name restricting input to only letters upper or lower case */
   for (loop=0;loop<entries;++loop)
   {
      printf("Entry %d/n", loop);
      printf("  Name   : ");
      scanf("%[A-Za-z]", entry[loop].name);
      fflush(stdin);  /* flush the input stream in case of bad input */

/* input an age as an integer */
      printf("  Age    : ");
      scanf("%d", &entry[loop].age);
      fflush(stdin);  /* flush the input stream in case of bad input */

/* input a salary as a float */
      printf("  Salary : ");
      scanf("%f", &entry[loop].salary);
      fflush(stdin); /* flush the input stream in case of bad input */
   }

/* Input a name, age and salary as a string, integer, and double */

   printf("/nPlease enter your name, age and salary/n");
   scanf("%20s %d %lf", name, &age, &salary);


/* Print out the data that was input */
   printf("/n/nTable %s/n",label);
   printf("Compiled by %s  age %d  $%15.2lf/n", name, age, salary);
   printf("-----------------------------------------------------/n");
   for (loop=0;loop<entries;++loop)
      printf("%4d  %-20s  %5d  %15.2lf/n",
         loop + 1,
  entry[loop].name,
  entry[loop].age,
  entry[loop].salary);
   printf("-----------------------------------------------------/n");
   return 0;
}



函数名: stat
功  能: 读取打开文件信息
用  法: int stat(char *pathname, struct stat *buff);
程序例:

#include <sys/stat.h>
#include <stdio.h>
#include <time.h>

#define FILENAME "TEST.$$$"

int main(void)
{
   struct stat statbuf;
   FILE *stream;

   /* open a file for update */
   if ((stream = fopen(FILENAME, "w+")) == NULL)
   {
      fprintf(stderr, "Cannot open output file./n");
      return(1);
   }

   /* get information about the file */
   stat(FILENAME, &statbuf);

   fclose(stream);

   /* display the information returned */
   if (statbuf.st_mode & S_IFCHR)
      printf("Handle refers to a device./n");
   if (statbuf.st_mode & S_IFREG)
      printf("Handle refers to an ordinary file./n");
   if (statbuf.st_mode & S_IREAD)

      printf("User has read permission on file./n");
   if (statbuf.st_mode & S_IWRITE)
      printf("User has write permission on file./n");

   printf("Drive letter of file: %c/n", 'A'+statbuf.st_dev);
   printf("Size of file in bytes: %ld/n", statbuf.st_size);
   printf("Time file last opened: %s/n", ctime(&statbuf.st_ctime));
   return 0;
}




函数名: _status87
功  能: 取浮点状态
用  法: unsigned int _status87(void);
程序例:

#include <stdio.h>
#include <float.h>

int main(void)
{
   float x;
   double y = 1.5e-100;

   printf("Status 87 before error: %x/n", _status87());

   x = y;  /* <-- force an error to occur */
   y = x;

   printf("Status 87 after error : %x/n", _status87());
   return 0;
}



函数名: stime
功  能: 设置时间
用  法: int stime(long *tp);
程序例:

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

int main(void)
{
   time_t t;
   struct tm *area;

   t = time(NULL);
   area = localtime(&t);
   printf("Number of seconds since 1/1/1970 is: %ld/n", t);
   printf("Local time is: %s", asctime(area));

   t++;
   area = localtime(&t);
   printf("Add a second:  %s", asctime(area));

   t += 60;
   area = localtime(&t);
   printf("Add a minute:  %s", asctime(area));

   t += 3600;

   area = localtime(&t);
   printf("Add an hour:   %s", asctime(area));

   t += 86400L;
   area = localtime(&t);
   printf("Add a day:     %s", asctime(area));

   t += 2592000L;
   area = localtime(&t);
   printf("Add a month:   %s", asctime(area));

   t += 31536000L;
   area = localtime(&t);
   printf("Add a year:    %s", asctime(area));
   return 0;
}




函数名: stpcpy
功  能: 拷贝一个字符串到另一个
用  法: char *stpcpy(char *destin, char *source);
程序例:

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

int main(void)
{
   char string[10];
   char *str1 = "abcdefghi";

   stpcpy(string, str1);
   printf("%s/n", string);
   return 0;
}




函数名: strcat
功  能: 字符串拼接函数
用  法: char *strcat(char *destin, char *source);
程序例:

#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;
}




函数名: strchr
功  能: 在一个串中查找给定字符的第一个匹配之处/
用  法: char *strchr(char *str, char c);
程序例:

#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;
}




函数名: strcmp
功  能: 串比较
用  法: int strcmp(char *str1, char *str2);
程序例:

#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;
}




函数名: strncmpi
功  能: 将一个串中的一部分与另一个串比较, 不管大小写
用  法: int strncmpi(char *str1, char *str2, unsigned maxlen);
程序例:

#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;
}




函数名: strcpy
功  能: 串拷贝
用  法: char *strcpy(char *str1, char *str2);
程序例:

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

int main(void)
{
    char string[10];
    char *str1 = "abcdefghi";

    strcpy(string, str1);
    printf("%s/n", string);
    return 0;
}




函数名: strcspn
功  能: 在串中查找第一个给定字符集内容的段
用  法: int strcspn(char *str1, char *str2);
程序例:

#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;
}




函数名: strdup
功  能: 将串拷贝到新建的位置处
用  法: char *strdup(char *str);
程序例:

#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;
}




函数名: stricmp
功  能: 以大小写不敏感方式比较两个串
用  法: int stricmp(char *str1, char *str2);
程序例:

#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;
}



函数名: strerror
功  能: 返回指向错误信息字符串的指针
用  法: char *strerror(int errnum);
程序例:

#include <stdio.h>
#include <errno.h>

int main(void)
{
   char *buffer;
   buffer = strerror(errno);
   printf("Error: %s/n", buffer);
   return 0;
}




函数名: strcmpi
功  能: 将一个串与另一个比较, 不管大小写
用  法: int strcmpi(char *str1, char *str2);
程序例:

#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;
}




函数名: strncmp
功  能: 串比较
用  法: int strncmp(char *str1, char *str2, int maxlen);
程序例:

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

int  main(void)

{
   char *buf1 = "aaabbb", *buf2 = "bbbccc", *buf3 = "ccc";
   int ptr;

   ptr = strncmp(buf2,buf1,3);
   if (ptr > 0)
      printf("buffer 2 is greater than buffer 1/n");
   else
      printf("buffer 2 is less than buffer 1/n");

   ptr = strncmp(buf2,buf3,3);
   if (ptr > 0)
      printf("buffer 2 is greater than buffer 3/n");
   else
      printf("buffer 2 is less than buffer 3/n");

   return(0);
}



函数名: strncmpi
功  能: 把串中的一部分与另一串中的一部分比较, 不管大小写
用  法: int strncmpi(char *str1, char *str2);
程序例:

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

int main(void)
{
   char *buf1 = "BBBccc", *buf2 = "bbbccc";
   int ptr;

   ptr = strncmpi(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;

}



函数名: strncpy
功  能: 串拷贝
用  法: char *strncpy(char *destin, char *source, int maxlen);
程序例:

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

int main(void)
{
   char string[10];
   char *str1 = "abcdefghi";

   strncpy(string, str1, 3);
   string[3] = '/0';
   printf("%s/n", string);
   return 0;
}



函数名: strnicmp
功  能: 不注重大小写地比较两个串
用  法: int strnicmp(char *str1, char *str2, unsigned maxlen);
程序例:

#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;
}




函数名: strnset
功  能: 将一个串中的所有字符都设为指定字符
用  法: char *strnset(char *str, char ch, unsigned n);
程序例:

#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;

}



函数名: strpbrk
功  能: 在串中查找给定字符集中的字符
用  法: char *strpbrk(char *str1, char *str2);
程序例:

#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;
}




函数名: strrchr
功  能: 在串中查找指定字符的最后一个出现
用  法: char *strrchr(char *str, char c);
程序例:

#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;
}




函数名: strrev
功  能: 串倒转
用  法: char *strrev(char *str);
程序例:

#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;
}


函数名: strset

功  能: 将一个串中的所有字符都设为指定字符
用  法: char *strset(char *str, char c);
程序例:

#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;
}




函数名: strspn
功  能: 在串中查找指定字符集的子集的第一次出现
用  法: int strspn(char *str1, char *str2);
程序例:

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

int main(void)
{
   char *string1 = "1234567890";
   char *string2 = "123DC8";
   int length;

   length = strspn(string1, string2);
   printf("Character where strings differ is at position %d/n", length);
   return 0;
}



函数名: strstr
功  能: 在串中查找指定字符串的第一次出现
用  法: char *strstr(char *str1, char *str2);
程序例:

#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;
}



函数名: strtod
功  能: 将字符串转换为double型值
用  法: double strtod(char *str, char **endptr);
程序例:

#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;
}




函数名: strtok
功  能: 查找由在第二个串中指定的分界符分隔开的单词
用  法: char *strtok(char *str1, char *str2);
程序例:

#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;
}




函数名: strtol
功  能: 将串转换为长整数
用  法: long strtol(char *str, char **endptr, int base);
程序例:

#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;
}


函数名: strupr
功  能: 将串中的小写字母转换为大写字母
用  法: char *strupr(char *str);
程序例:

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

int main(void)
{
   char *string = "abcdefghijklmnopqrstuvwxyz", *ptr;

   /* converts string to upper case characters */
   ptr = strupr(string);
   printf("%s/n", ptr);
   return 0;
}




函数名: swab
功  能: 交换字节
用  法: void swab (char *from, char *to, int nbytes);
程序例:

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

char source[15] = "rFna koBlrna d";
char target[15];

int main(void)
{
   swab(source, target, strlen(source));
   printf("This is target: %s/n", target);
   return 0;
}




函数名: system
功  能: 发出一个DOS命令
用  法: int system(char *command);
程序例:

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

int main(void)
{
   printf("About to spawn command.com and run a DOS command/n");
   system("dir");
   return 0;
}

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