c_info.txt

这是一个unix 系统下的 C 语言函数大全的电子文章。

      } 


      函数名: detectgraph 
      功 能: 通过检测硬件确定图形驱动程序和模式 
      用 法: void far detectgraph(int far *graphdriver, int far 
      *graphmode); 
      程序例: 

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

      /* names of the various cards supported */ 
      char *dname[] = { "requests detection", 
      "a CGA", 
      "an MCGA", 
      "an EGA", 
      "a 64K EGA", 
      "a monochrome EGA", 
      "an IBM 8514", 
      "a Hercules monochrome", 
      "an AT&T 6300 PC", 
      "a VGA", 
      "an IBM 3270 PC" 
      }; 

      int main(void) 
      { 
      /* returns detected hardware info. */ 
      int gdriver, gmode, errorcode; 

      /* detect graphics hardware available */ 
      detectgraph(&gdriver, &gmode); 

      /* read result of detectgraph call */ 
      errorcode = graphresult(); 
      if (errorcode != grOk) /* an error 
      occurred */ 
      { 
      printf("Graphics error: %s\n", \ 
      grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); /* terminate with an error 
      code */ 
      } 

      /* display the information detected */ 
      clrscr(); 
      printf("You have %s video display \ 
      card.\n", dname[gdriver]); 
      printf("Press any key to halt:"); 
      getch(); 
      return 0; 
      } 




      函数名: difftime 
      功 能: 计算两个时刻之间的时间差 
      用 法: double difftime(time_t time2, time_t time1); 
      程序例: 

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

      int main(void) 
      { 
      time_t first, second; 

      clrscr(); 
      first = time(NULL); /* Gets system 
      time */ 
      delay(2000); /* Waits 2 secs */ 
      second = time(NULL); /* Gets system time 
      again */ 

      printf("The difference is: %f \ 
      seconds\n",difftime(second,first)); 
      getch(); 

      return 0; 
      } 



      函数名: disable 
      功 能: 屏蔽中断 
      用 法: void disable(void); 
      程序例: 

      /***NOTE: This is an interrupt service 
      routine. You cannot compile this program 
      with Test Stack Overflow turned on and 
      get an executable file that operates 
      correctly. */ 

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

      #define INTR 0X1C /* The clock tick 
      interrupt */ 

      void interrupt ( *oldhandler)(void); 

      int count=0; 

      void interrupt handler(void) 
      { 
      /* disable interrupts during the handling of 
      the interrupt */ 
      disable(); 
      /* increase the global counter */ 
      count++; 
      /* reenable interrupts at the end of the 
      handler */ 
      enable(); 
      /* call the old routine */ 
      oldhandler(); 
      } 

      int main(void) 
      { 
      /* save the old interrupt vector */ 
      oldhandler = getvect(INTR); 

      /* install the new interrupt handler */ 
      setvect(INTR, handler); 

      /* loop until the counter exceeds 20 */ 
      while (count < 20) 
      printf("count is %d\n",count); 

      /* reset the old interrupt handler */ 
      setvect(INTR, oldhandler); 

      return 0; 
      } 

      函数名: div 
      功 能: 将两个整数相除, 返回商和余数 
      用 法: div_t (int number, int denom); 
      程序例: 

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

      div_t x; 

      int main(void) 
      { 
      x = div(10,3); 
      printf("10 div 3 = %d remainder %d\n", x.quot, x.rem); 

      return 0; 
      } 



      函数名: dosexterr 
      功 能: 获取扩展DOS错误信息 
      用 法: int dosexterr(struct DOSERR *dblkp); 
      程序例: 

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

      int main(void) 
      { 
      FILE *fp; 
      struct DOSERROR info; 

      fp = fopen("perror.dat","r"); 
      if (!fp) perror("Unable to open file for 
      reading"); 
      dosexterr(&info); 

      printf("Extended DOS error \ 
      information:\n"); 
      printf(" Extended error: \ 
      %d\n",info.exterror); 
      printf(" Class: \ 
      %x\n",info.class); 
      printf(" Action: \ 
      %x\n",info.action); 
      printf(" Error Locus: \ 
      %x\n",info.locus); 

      return 0; 
      } 



      函数名: dostounix 
      功 能: 转换日期和时间为UNIX时间格式 
      用 法: long dostounix(struct date *dateptr, struct time 
      *timeptr); 
      程序例: 

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

      int main(void) 
      { 
      time_t t; 
      struct time d_time; 
      struct date d_date; 
      struct tm *local; 

      getdate(&d_date); 
      gettime(&d_time); 

      t = dostounix(&d_date, &d_time); 
      local = localtime(&t); 
      printf("Time and Date: %s\n", \ 
      asctime(local)); 

      return 0; 
      } 



      函数名: drawpoly 
      功 能: 画多边形 
      用 法: void far drawpoly(int numpoints, int far *polypoints); 
      程序例: 

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

      int main(void) 
      { 
      /* request auto detection */ 
      int gdriver = DETECT, gmode, errorcode; 
      int maxx, maxy; 

      /* our polygon array */ 
      int poly[10]; 

      /* initialize graphics and local 
      variables */ 
      initgraph(&gdriver, &gmode, ""); 

      /* read result of initialization */ 
      errorcode = graphresult(); 
      if (errorcode != grOk) 
      /* an error occurred */ 
      { 
      printf("Graphics error: %s\n", \ 
      grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      /* terminate with an error code */ 
      exit(1); 
      } 

      maxx = getmaxx(); 
      maxy = getmaxy(); 

      poly[0] = 20; /* 1st vertext */ 
      poly[1] = maxy / 2; 

      poly[2] = maxx - 20; /* 2nd */ 
      poly[3] = 20; 

      poly[4] = maxx - 50; /* 3rd */ 
      poly[5] = maxy - 20; 

      poly[6] = maxx / 2; /* 4th */ 
      poly[7] = maxy / 2; 
      /* 
      drawpoly doesn't automatically close 
      the polygon, so we close it. 
      */ 
      poly[8] = poly[0]; 
      poly[9] = poly[1]; 

      /* draw the polygon */ 
      drawpoly(5, poly); 

      /* clean up */ 
      getch(); 
      closegraph(); 
      return 0; 
      } 



      函数名: dup 
      功 能: 复制一个文件句柄 
      用 法: int dup(int handle); 
      程序例: 

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

      void flush(FILE *stream); 

      int main(void) 
      { 
      FILE *fp; 
      char msg[] = "This is a test"; 

      /* create a file */ 
      fp = fopen("DUMMY.FIL", "w"); 

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

      clrscr(); 
      printf("Press any key to flush \ 
      DUMMY.FIL:"); 
      getch(); 

      /* flush the data to DUMMY.FIL without 
      closing it */ 
      flush(fp); 

      printf("\nFile was flushed, Press any \ 
      key to quit:"); 
      getch(); 
      return 0; 
      } 

      void flush(FILE *stream) 
      { 
      int duphandle; 

      /* flush TC's internal buffer */ 
      fflush(stream); 

      /* make a duplicate file handle */ 
      duphandle = dup(fileno(stream)); 

      /* close the duplicate handle to flush the 
      DOS buffer */ 
      close(duphandle); 
      } 



      函数名: dup2 
      功 能: 复制文件句柄 
      用 法: int dup2(int oldhandle, int newhandle); 
      程序例: 

      #include <sys\stat.h> 
      #include <string.h> 
      #include <fcntl.h> 
      #include <io.h> 

      int main(void) 
      { 
      #define STDOUT 1 

      int nul, oldstdout; 
      char msg[] = "This is a test"; 

      /* create a file */ 
      nul = open("DUMMY.FIL", O_CREAT | O_RDWR, 
      S_IREAD | S_IWRITE); 

      /* create a duplicate handle for standard 
      output */ 
      oldstdout = dup(STDOUT); 
      /* 
      redirect standard output to DUMMY.FIL 
      by duplicating the file handle onto the 
      file handle for standard output. 
      */ 
      dup2(nul, STDOUT); 

      /* close the handle for DUMMY.FIL */ 
      close(nul); 

      /* will be redirected into DUMMY.FIL */ 
      write(STDOUT, msg, strlen(msg)); 

      /* restore original standard output 
      handle */ 
      dup2(oldstdout, STDOUT); 

      /* close duplicate handle for STDOUT */ 
      close(oldstdout); 

      return 0; 
      } 
      函数名: ecvt 
      功 能: 把一个浮点数转换为字符串 
      用 法: char ecvt(double value, int ndigit, int *decpt, int 
      *sign); 
      程序例: 

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

      int main(void) 
      { 
      char *string; 
      double value; 
      int dec, sign; 
      int ndig = 10; 

      clrscr(); 
      value = 9.876; 
      string = ecvt(value, ndig, &dec, &sign); 
      printf("string = %s dec = %d \ 
      sign = %d\n", string, dec, sign); 

      value = -123.45; 
      ndig= 15; 
      string = ecvt(value,ndig,&dec,&sign); 
      printf("string = %s dec = %d sign = %d\n", 
      string, dec, sign); 


      value = 0.6789e5; /* scientific 
      notation */ 
      ndig = 5; 
      string = ecvt(value,ndig,&dec,&sign); 
      printf("string = %s dec = %d\ 
      sign = %d\n", string, dec, sign); 

      return 0; 
      } 



      函数名: ellipse 
      功 能: 画一椭圆 
      用 法: void far ellipse(int x, int y, int stangle, int endangle, 

      int xradius, int yradius); 
      程序例: 

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

      int main(void) 
      { 
      /* request auto detection */ 
      int gdriver = DETECT, gmode, errorcode; 
      int midx, midy; 
      int stangle = 0, endangle = 360; 
      int xradius = 100, yradius = 50; 

      /* initialize graphics, local variables */ 
      initgraph(&gdriver, &gmode, ""); 

      /* read result of initialization */ 
      errorcode = graphresult(); 
      if (errorcode != grOk) 
      /* an error occurred */ 
      { 
      printf("Graphics error: %s\n", 
      grapherrormsg(errorcode)); 
      printf("Press any key to halt:"); 
      getch(); 
      exit(1); 
      /* terminate with an error code */ 
      } 

      midx = getmaxx() / 2; 
      midy = getmaxy() / 2; 
      setcolor(getmaxcolor()); 

      /* draw ellipse */ 
      ellipse(midx, midy, stangle, endangle, 
      xradius, yradius); 

      /* clean up */ 
      getch(); 
      closegraph(); 
      return 0; 
      } 



      函数名: enable 
      功 能: 开放硬件中断 
      用 法: void enable(void); 
      程序例: 

      /* ** NOTE: 
      This is an interrupt service routine. You can NOT compile this 
      program 
      with Test Stack Overflow turned on and get an executable file 
      which will 
      operate correctly. 
      */ 

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

      /* The clock tick interrupt */ 
      #define INTR 0X1C 

      void interrupt ( *oldhandler)(void); 

      int count=0; 

      void interrupt handler(void) 
      { 
      /* 
      disable interrupts during the handling of the interrupt 
      */ 
      disable(); 
      /* increase the global counter */ 
      count++; 
      /* 
      re enable interrupts at the end of the handler 
      */ 
      enable(); 
      /* call the old routine */ 
      oldhandler(); 
      } 

      int main(void) 
      { 
      /* save the old interrupt vector */ 
      oldhandler = getvect(INTR); 

      /* install the new interrupt handler */ 
      setvect(INTR, handler); 

      /* loop until the counter exceeds 20 */ 
      while (count < 20) 
      printf("count is %d\n",count); 

      /* reset the old interrupt handler */ 
      setvect(INTR, oldhandler); 

      return 0; 
      } 



      函数名: eof 
      功 能: 检测文件结束 
      用 法: int eof(int *handle); 
      程序例: 

      #include <sys\stat.h> 
      #include <string.h> 
      #include <stdio.h> 
      #include <fcntl.h> 
      #include <io.h> 

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

      /* create a file */ 
      handle = open("DUMMY.FIL", 
      O_CREAT | O_RDWR, 
      S_IREAD | S_IWRITE); 

      /* write some data to the file */ 
      write(handle, msg, strlen(msg)); 

      /* seek to the beginning of the file */ 
      lseek(handle, 0L, SEEK_SET); 

      /* 
      reads chars from the file until hit EOF 
      */ 
      do 
      { 
      read(handle, &ch, 1); 
      printf("%c", ch); 
      } while (!eof(handle)); 

      close(handle); 
      return 0; 
      } 



      函数名: exec... 
      功 能: 装入并运行其它程序的函数 
      用 法: int execl(char *pathname, char *arg0, arg1, ..., argn, 
      NULL); 
      int execle(char *pathname, char *arg0, arg1, ..., argn, NULL, 
      char *envp[]); 
      int execlp(char *pathname, char *arg0, arg1, .., NULL); 
      int execple(char *pathname, char *arg0, arg1, ..., NULL, 
      char *envp[]); 
      int execv(char *pathname, char *argv[]); 
      int execve(char *pathname, char *argv[], char *envp[]); 
      int execvp(char *pathname, char *argv[]); 
      int execvpe(char *pathname, char *argv[], char *envp[]);