c_info.txt

这是一个unix 系统下的 C 语言函数大全的电子文章。

C语言库函数---unix常用系统调用---使用说明 

      ChinaUnix.net首页 -> 论坛首页 -> C/C++
发表于: 2003-05-20 11:04    发表主题: C语言库函数---unix常用系统调用---使用说明  



【说明】 
一共分为3个小节，1小节给定一个连接，该连接给了一些常用标准c的函数使用说明，但是不够全面。2小结按字母顺序排列，几乎覆盖了c中常用的函数，同时有些函数不在unix系统中支持了。3小节描述了unix系统中常用系统调用的使用说明。 



1、【下面这个连接给出了一些c库的函数说明使用例程，但是不够全面，可以作为参考】 
http://www.ggv.com.cn/forum/clib/clib.html 

2、【如下对C语言库函数按字母顺序描述,如果上面连接中找不到，可以到这里查找到，需要说明的是，有些函数在新的libc中已经不提供了，如果要查找unix系统常用系统调用函数使用说明，请到小节3查找】 

      代码:

      函数名: abort 
      功 能: 异常终止一个进程 
      用 法: void abort(void); 
      程序例: 
      #include <stdio.h> 
      #include <stdlib.h> 
      int main(void) 
      { 
      printf("Calling abort()\n"); 
      abort(); 
      return 0; /* This is never reached */ 
      } 



      函数名: abs 
      功 能: 求整数的绝对值 
      用 法: int abs(int i); 
      程序例: 
      #include <stdio.h> 
      #include <math.h> 

      int main(void) 
      { 
      int number = -1234; 

      printf("number: %d absolute value: %d\n", number, 
      abs(number)); 
      return 0; 
      } 



      函数名: absread, abswirte 
      功 能: 绝对磁盘扇区读、写数据 
      用 法: int absread(int drive, int nsects, int sectno, void 
      *buffer); 
      int abswrite(int drive, int nsects, in tsectno, void *buffer); 

      程序例: 
      /* absread example */ 

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

      int main(void) 
      { 
      int i, strt, ch_out, sector; 
      char buf[512]; 

      printf("Insert a diskette into drive A and press any key\n"); 
      getch(); 
      sector = 0; 
      if (absread(0, 1, sector, &buf) != 0) 
      { 
      perror("Disk problem"); 
      exit(1); 
      } 
      printf("Read OK\n"); 
      strt = 3; 
      for (i=0; i<80; i++) 
      { 
      ch_out = buf[strt+i]; 
      putchar(ch_out); 
      } 
      printf("\n"); 
      return(0); 
      } 




      函数名: access 
      功 能: 确定文件的访问权限 
      用 法: int access(const char *filename, int amode); 
      程序例: 
      #include <stdio.h> 
      #include <io.h> 

      int file_exists(char *filename); 

      int main(void) 
      { 
      printf("Does NOTEXIST.FIL exist: %s\n", 
      file_exists("NOTEXISTS.FIL") ? "YES" : "NO"); 
      return 0; 
      } 

      int file_exists(char *filename) 
      { 
      return (access(filename, 0) == 0); 
      } 


      函数名: acos 
      功 能: 反余弦函数 
      用 法: double acos(double x); 
      程序例: 
      #include <stdio.h> 
      #include <math.h> 

      int main(void) 
      { 
      double result; 
      double x = 0.5; 

      result = acos(x); 
      printf("The arc cosine of %lf is %lf\n", x, result); 
      return 0; 
      } 



      函数名: allocmem 
      功 能: 分配DOS存储段 
      用 法: int allocmem(unsigned size, 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 == -1) 
      printf("Allocated memory at segment: %x\n", segp); 
      else 
      printf("Failed: maximum number of paragraphs available is 
      %u\n", 
      stat); 

      return 0; 
      } 



      函数名: arc 
      功 能: 画一弧线 
      用 法: void far arc(int x, int y, int stangle, int endangle, int 
      radius); 
      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 = 45, endangle = 135; 
      int radius = 100; 

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

      /* read result of initialization */ 
      errorcode = graphresult(); /* an error occurred */ 
      if (errorcode != grOk) 
      { 
      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 arc */ 
      arc(midx, midy, stangle, endangle, radius); 

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



      函数名: asctime 
      功 能: 转换日期和时间为ASCII码 
      用 法: char *asctime(const struct tm *tblock); 
      程序例: 
      #include <stdio.h> 
      #include <string.h> 
      #include <time.h> 

      int main(void) 
      { 
      struct tm t; 
      char str[80]; 

      /* sample loading of tm structure */ 

      t.tm_sec = 1; /* Seconds */ 
      t.tm_min = 30; /* Minutes */ 
      t.tm_hour = 9; /* Hour */ 
      t.tm_mday = 22; /* Day of the Month */ 
      t.tm_mon = 11; /* Month */ 
      t.tm_year = 56; /* Year - does not include century */ 
      t.tm_wday = 4; /* Day of the week */ 
      t.tm_yday = 0; /* Does not show in asctime */ 
      t.tm_isdst = 0; /* Is Daylight SavTime; does not show in 
      asctime */ 

      /* converts structure to null terminated 
      string */ 

      strcpy(str, asctime(&t)); 
      printf("%s\n", str); 

      return 0; 
      } 




      函数名: asin 
      功 能: 反正弦函数 
      用 法: double asin(double x); 
      程序例: 
      #include <stdio.h> 
      #include <math.h> 

      int main(void) 
      { 
      double result; 
      double x = 0.5; 

      result = asin(x); 
      printf("The arc sin of %lf is %lf\n", x, result); 
      return(0); 
      } 




      函数名: assert 
      功 能: 测试一个条件并可能使程序终止 
      用 法: void assert(int test); 
      程序例: 
      #include <assert.h> 
      #include <stdio.h> 
      #include <stdlib.h> 

      struct ITEM { 
      int key; 
      int value; 
      }; 

      /* add item to list, make sure list is not null */ 
      void additem(struct ITEM *itemptr) { 
      assert(itemptr != NULL); 
      /* add item to list */ 
      } 

      int main(void) 
      { 
      additem(NULL); 
      return 0; 
      } 




      函数名: atan 
      功 能: 反正切函数 
      用 法: double atan(double x); 
      程序例: 
      #include <stdio.h> 
      #include <math.h> 

      int main(void) 
      { 
      double result; 
      double x = 0.5; 

      result = atan(x); 
      printf("The arc tangent of %lf is %lf\n", x, result); 
      return(0); 
      } 



      函数名: atan2 
      功 能: 计算Y/X的反正切值 
      用 法: double atan2(double y, double x); 
      程序例: 
      #include <stdio.h> 
      #include <math.h> 

      int main(void) 
      { 
      double result; 
      double x = 90.0, y = 45.0; 

      result = atan2(y, x); 
      printf("The arc tangent ratio of %lf is %lf\n", (y / x), 
      result); 
      return 0; 
      } 



      函数名: atexit 
      功 能: 注册终止函数 
      用 法: int atexit(atexit_t func); 
      程序例: 
      #include <stdio.h> 
      #include <stdlib.h> 

      void exit_fn1(void) 
      { 
      printf("Exit function #1 called\n"); 
      } 

      void exit_fn2(void) 
      { 
      printf("Exit function #2 called\n"); 
      } 

      int main(void) 
      { 
      /* post exit function #1 */ 
      atexit(exit_fn1); 
      /* post exit function #2 */ 
      atexit(exit_fn2); 
      return 0; 
      } 




      函数名: atof 
      功 能: 把字符串转换成浮点数 
      用 法: double atof(const char *nptr); 
      程序例: 
      #include <stdlib.h> 
      #include <stdio.h> 

      int main(void) 
      { 
      float f; 
      char *str = "12345.67"; 

      f = atof(str); 
      printf("string = %s float = %f\n", str, f); 
      return 0; 
      } 



      函数名: atoi 
      功 能: 把字符串转换成长整型数 
      用 法: int atoi(const char *nptr); 
      程序例: 
      #include <stdlib.h> 
      #include <stdio.h> 

      int main(void) 
      { 
      int n; 
      char *str = "12345.67"; 

      n = atoi(str); 
      printf("string = %s integer = %d\n", str, n); 
      return 0; 
      } 



      函数名: atol 
      功 能: 把字符串转换成长整型数 
      用 法: long atol(const char *nptr); 
      程序例: 

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

      int main(void) 
      { 
      long l; 
      char *str = "98765432"; 

      l = atol(lstr); 
      printf("string = %s integer = %ld\n", str, l); 
      return(0); 
      } 
      函数名: bar 
      功 能: 画一个二维条形图 
      用 法: void far bar(int left, int top, int right, int bottom); 
      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, i; 

      /* 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(); 
      exit(1); /* terminate with an error code */ 
      } 

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

      /* loop through the fill patterns */ 
      for (i=SOLID_FILL; i<USER_FILL; i++) 
      { 
      /* set the fill style */ 
      setfillstyle(i, getmaxcolor()); 

      /* draw the bar */ 
      bar(midx-50, midy-50, midx+50, 
      midy+50); 

      getch(); 
      } 

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




      函数名: bar3d 
      功 能: 画一个三维条形图 
      用 法: void far bar3d(int left, int top, int right, int bottom, 
      int depth, int topflag); 
      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, i; 

      /* 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 error code */ 
      } 

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

      /* loop through the fill patterns */ 
      for (i=EMPTY_FILL; i<USER_FILL; i++) 
      { 
      /* set the fill style */ 
      setfillstyle(i, getmaxcolor()); 

      /* draw the 3-d bar */ 
      bar3d(midx-50, midy-50, midx+50, midy+50, 10, 1); 

      getch(); 
      } 

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




      函数名: bdos 
      功 能: DOS系统调用 
      用 法: int bdos(int dosfun, unsigned dosdx, unsigned dosal); 
      程序例: 

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

      /* Get current drive as 'A', 'B', ... */ 
      char current_drive(void) 
      { 
      char curdrive; 

      /* Get current disk as 0, 1, ... */ 
      curdrive = bdos(0x19, 0, 0); 
      return('A' + curdrive); 
      } 

      int main(void) 
      { 
      printf("The current drive is %c:\n", current_drive()); 
      return 0; 
      } 




      函数名: bdosptr 
      功 能: DOS系统调用 
      用 法: int bdosptr(int dosfun, void *argument, unsigned dosal); 
      程序例: 

      #include <string.h> 
      #include <stdio.h> 
      #include <dir.h> 
      #include <dos.h> 
      #include <errno.h> 
      #include <stdlib.h> 

      #define BUFLEN 80 

      int main(void) 
      { 
      char buffer[BUFLEN]; 
      int test; 

      printf("Enter full pathname of a directory\n"); 
      gets(buffer); 

      test = bdosptr(0x3B,buffer,0); 
      if(test) 
      { 
      printf("DOS error message: %d\n", errno); 
      /* See errno.h for error listings */ 
      exit (1); 
      } 

      getcwd(buffer, BUFLEN); 
      printf("The current directory is: %s\n", buffer); 

      return 0; 
      } 




      函数名: bioscom 
      功 能: 串行I/O通信 
      用 法: int bioscom(int cmd, char abyte, int port); 
      程序例: 

      #include <bios.h> 
      #include <conio.h> 

      #define COM1 0 
      #define DATA_READY 0x100 
      #define TRUE 1 
      #define FALSE 0 

      #define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00) 

      int main(void) 
      { 
      int in, out, status, DONE = FALSE; 

      bioscom(0, SETTINGS, COM1); 
      cprintf("... BIOSCOM [ESC] to exit ...\n");