数学函数2.txt

一些用到的函数 功能齐全

    getcwd(s,MAXPATH);              /* get the current working directory */ 
    strcat(s,"\\");                  /* append on a trailing \ character */ 
    fnsplit(s,drive,dir,file,ext); /* split the string to separate elems */ 
    strcpy(file,"DATA"); 
    strcpy(ext,".TXT"); 
    fnmerge(s,drive,dir,file,ext);   /* merge everything into one string */ 
    puts(s);                                 /* display resulting string */ 

    return 0; 
} 
  
  
  

函数名: fopen 
功  能: 打开一个流 
用  法: FILE *fopen(char *filename, char *type); 
程序例: 

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

int main(void) 
{ 
    char *s; 
    char drive[MAXDRIVE]; 
    char dir[MAXDIR]; 
    char file[MAXFILE]; 
    char ext[MAXEXT]; 
    int flags; 

    s=getenv("COMSPEC"); /* get the comspec environment parameter */ 
    flags=fnsplit(s,drive,dir,file,ext); 

    printf("Command processor info:\n"); 
    if(flags & DRIVE) 
       printf("\tdrive: %s\n",drive); 
    if(flags & DIRECTORY) 
       printf("\tdirectory: %s\n",dir); 
    if(flags & FILENAME) 
       printf("\tfile: %s\n",file); 
    if(flags & EXTENSION) 
       printf("\textension: %s\n",ext); 

    return 0; 
} 
  

函数名: fprintf 
功  能: 传送格式化输出到一个流中 
用  法: int fprintf(FILE *stream, char *format[, argument,...]); 
程序例: 

/* Program to create backup of the 
   AUTOEXEC.BAT file */ 

#include <stdio.h> 

int main(void) 
{ 
   FILE *in, *out; 

   if ((in = fopen("\\AUTOEXEC.BAT", "rt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open input \ 
       file.\n"); 
      return 1; 
   } 

   if ((out = fopen("\\AUTOEXEC.BAK", "wt")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open output \ 
       file.\n"); 
      return 1; 
   } 

   while (!feof(in)) 
      fputc(fgetc(in), out); 

   fclose(in); 
   fclose(out); 
   return 0; 
} 
  
  
  

函数名: FP_OFF 
功  能: 获取远地址偏移量 
用  法: unsigned FP_OFF(void far *farptr); 
程序例: 

/* FP_OFF */ 

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

int main(void) 
{ 
   char *str = "fpoff.c"; 

   printf("The offset of this file in memory\ 
          is: %Fp\n", FP_OFF(str)); 

   return 0; 
} 
  
  

函数名: FP_SEG 
功  能: 获取远地址段值 
用  法: unsigned FP_SEG(void far *farptr); 
程序例: 

/* FP_SEG */ 

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

int main(void) 
{ 
   char *filename = "fpseg.c"; 

   printf("The offset of this file in memory\ 
   is: %Fp\n", FP_SEG(filename)); 

   return(0); 
} 
  
  
  

函数名: fputc 
功  能: 送一个字符到一个流中 
用  法: int fputc(int ch, FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   char msg[] = "Hello world"; 
   int i = 0; 

   while (msg[i]) 
   { 
      fputc(msg[i], stdout); 
      i++; 
   } 
   return 0; 
} 
  
  
  

函数名: fputchar 
功  能: 送一个字符到标准输出流(stdout)中 
用  法: int fputchar(char ch); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   char msg[] = "This is a test"; 
   int i = 0; 

   while (msg[i]) 
   { 
      fputchar(msg[i]); 
      i++; 
   } 
   return 0; 
} 
  
  
  

函数名: fputs 
功  能: 送一个字符到一个流中 
用  法: int fputs(char *string, FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   /* write a string to standard output */ 
   fputs("Hello world\n", stdout); 

   return 0; 
} 
  
  
  

函数名: fread 
功  能: 从一个流中读数据 
用  法: int fread(void *ptr, int size, int nitems, FILE *stream); 
程序例: 

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

int main(void) 
{ 
   FILE *stream; 
   char msg[] = "this is a test"; 
   char buf[20]; 

   if ((stream = fopen("DUMMY.FIL", "w+")) 
       == NULL) 
   { 
      fprintf(stderr, 
              "Cannot open output file.\n"); 
      return 1; 
   } 

   /* write some data to the file */ 
   fwrite(msg, strlen(msg)+1, 1, stream); 

   /* seek to the beginning of the file */ 
   fseek(stream, SEEK_SET, 0); 

   /* read the data and display it */ 
   fread(buf, strlen(msg)+1, 1, stream); 
   printf("%s\n", buf); 

   fclose(stream); 
   return 0; 
} 
  
  

函数名: free 
功  能: 释放已分配的块 
用  法: void free(void *ptr); 
程序例: 

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

int main(void) 
{ 
   char *str; 

   /* allocate memory for string */ 
   str = malloc(10); 

   /* copy "Hello" to string */ 
   strcpy(str, "Hello"); 

   /* display string */ 
   printf("String is %s\n", str); 

   /* free memory */ 
   free(str); 

   return 0; 
} 
  

函数名: freemem 
功  能: 释放先前分配的DOS内存块 
用  法: int freemem(unsigned seg); 
程序例: 

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

int main(void) 
{ 
   unsigned int size, segp; 
   int stat; 

   size = 64; /* (64 x 16) = 1024 bytes */ 
   stat = allocmem(size, &segp); 
   if (stat < 0) 
      printf("Allocated memory at segment:\ 
      %x\n", segp); 
   else 
      printf("Failed: maximum number of\ 
      paragraphs available is %u\n", 
      stat); 
   freemem(segp); 

   return 0; 
} 
  
  

函数名: freopen 
功  能: 替换一个流 
用  法: FILE *freopen(char *filename, char *type, FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   /* redirect standard output to a file */ 
   if (freopen("OUTPUT.FIL", "w", stdout) 
       == NULL) 
      fprintf(stderr, "error redirecting\ 
              stdout\n"); 

   /* this output will go to a file */ 
   printf("This will go into a file."); 

   /* close the standard output stream */ 
   fclose(stdout); 

   return 0; 
} 
  
  
  

函数名: frexp 
功  能: 把一个双精度数分解为尾数的指数 
用  法: double frexp(double value, int *eptr); 
程序例: 

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

int main(void) 
{ 
   double mantissa, number; 
   int exponent; 

   number = 8.0; 
   mantissa = frexp(number, &exponent); 

   printf("The number %lf is ", number); 
   printf("%lf times two to the ", mantissa); 
   printf("power of %d\n", exponent); 

   return 0; 
} 
  
  

函数名: fscanf 
功  能: 从一个流中执行格式化输入 
用  法: int fscanf(FILE *stream, char *format[,argument...]); 
程序例: 

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

int main(void) 
{ 
   int i; 

   printf("Input an integer: "); 

   /* read an integer from the 
      standard input stream */ 
   if (fscanf(stdin, "%d", &i)) 
      printf("The integer read was: %i\n", 
             i); 
   else 
   { 
      fprintf(stderr, "Error reading an \ 
              integer from stdin.\n"); 
      exit(1); 
   } 
   return 0; 
} 
  
  
  

函数名: fseek 
功  能: 重定位流上的文件指针 
用  法: int fseek(FILE *stream, long offset, int fromwhere); 
程序例: 

#include <stdio.h> 

long filesize(FILE *stream); 

int main(void) 
{ 
   FILE *stream; 

   stream = fopen("MYFILE.TXT", "w+"); 
   fprintf(stream, "This is a test"); 
   printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream)); 
   fclose(stream); 
   return 0; 
} 

long filesize(FILE *stream) 
{ 
   long curpos, length; 

   curpos = ftell(stream); 
   fseek(stream, 0L, SEEK_END); 
   length = ftell(stream); 
   fseek(stream, curpos, SEEK_SET); 
   return length; 
} 
  
  
  
  
  

函数名: fsetpos 
功  能: 定位流上的文件指针 
用  法: int fsetpos(FILE *stream, const fpos_t *pos); 
程序例: 

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

void showpos(FILE *stream); 

int main(void) 
{ 
   FILE *stream; 
   fpos_t filepos; 

   /* open a file for update */ 
   stream = fopen("DUMMY.FIL", "w+"); 

   /* save the file pointer position */ 
   fgetpos(stream, &filepos); 

   /* write some data to the file */ 
   fprintf(stream, "This is a test"); 

   /* show the current file position */ 
   showpos(stream); 

   /* set a new file position, display it */ 
   if (fsetpos(stream, &filepos) == 0) 
     showpos(stream); 
   else 
   { 
      fprintf(stderr, "Error setting file \ 
       pointer.\n"); 
      exit(1); 
   } 

   /* close the file */ 
   fclose(stream); 
   return 0; 
} 

void showpos(FILE *stream) 
{ 
   fpos_t pos; 

   /* display the current file pointer 
      position of a stream */ 
   fgetpos(stream, &pos); 
   printf("File position: %ld\n", pos); 
} 
  

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

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

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

   /* open a file for update */ 
   if ((stream = fopen("DUMMY.FIL", "w+")) 
       == NULL) 
   { 
      fprintf(stderr, "Cannot open output \ 
              file.\n"); 
      return(1); 
   } 
   fprintf(stream, "This is a test"); 
   fflush(stream); 

   /* get information about the file */ 
   fstat(fileno(stream), &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: ftell 
功  能: 返回当前文件指针 
用  法: long ftell(FILE *stream); 
程序例: 

#include <stdio.h> 

int main(void) 
{ 
   FILE *stream; 

   stream = fopen("MYFILE.TXT", "w+"); 
   fprintf(stream, "This is a test"); 
   printf("The file pointer is at byte \ 
          %ld\n", ftell(stream)); 
   fclose(stream); 
   return 0; 
} 
  
  
  

函数名: fwrite 
功  能: 写内容到流中 
用  法: int fwrite(void *ptr, int size, int nitems, FILE *stream); 
程序例: 

#include <stdio.h> 

struct mystruct 
{ 
  int i; 
  char ch; 
}; 

int main(void) 
{ 
   FILE *stream; 
   struct mystruct s; 

   if ((stream = fopen("TEST.$$$", "wb")) == NULL) /* open file TEST.$$$ */ 
   { 
      fprintf(stderr, "Cannot open output file.\n"); 
      return 1; 
   } 
   s.i = 0; 
   s.ch = 'A'; 
   fwrite(&s, sizeof(s), 1, stream); /* write struct s to file */ 
   fclose(stream); /* close file */ 
   return 0; 
} 
  

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