Linux系統編程4標準IO - fgetc和fputc

實驗1 以字符拷貝的方式，fgetc，fputc 實現 cp 命令，mycpy，格式是 ./mycpy srcfile destfile

實驗2 利用 fgetc()查看一個文件中有多少個有效字符

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1 字符的輸入 fgetc, getc, getchar

字符的輸入：fgetc, getc, getchar

NAME
fgetc, getc, getchar, - input of characters ,字符的輸入

SYNOPSIS
#include <stdio.h>

   int fgetc(FILE *stream); //以整型來接收讀到的字符
   int getc(FILE *stream);  //以整型來接收讀到的字符
   int getchar(void);

DESCRIPTION

fgetc() reads the next character from stream and returns it as an unsigned char cast to an int, or EOF on end of file or error.

從任何成功打開的流中獲取內容，包括標準輸入以及已經存在的文件中。fgetc()會被定義成函數來使用，以整型來接收讀到的字符

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getc() is equivalent to fgetc() except that it may be implemented as a macro which evaluates stream more than once.
從任何成功打開的流中獲取內容，包括標準輸入以及已經存在的文件中。getc()會被定義成宏使用

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getchar() is equivalent to getc(stdin).
從標準輸入讀入一個字符（函數參數是標準輸入，即終端）

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返回值

fgetc(), getc() and getchar() return the character read as an unsigned char cast to an int or EOF on end of file or error.

返回 以整型來接收讀到的字符，讀到文件尾端或者讀取失敗則返回 EOF

注意：函數和宏的區別：
內核鏈表通篇都是宏來實現的，除了inline內聯函數就是宏，沒有用函數，這樣做的目的是節約時間，宏不佔用調用時間，只佔用編譯時間。函數的調動 只佔用調用時間，不佔用編譯時間。內核這樣的實現是爲了節約時間，在對時間要求非常高的情況，如汽車的安全氣囊，是不允許氣囊晚一點點時間彈出來的。

2 字符的輸出：fputc，fputc，putchar

NAME
fputc, putc, putchar - output of characters，字符的輸出

SYNOPSIS
#include <stdio.h>

   int fputc(int c, FILE *stream);
   int putc(int c, FILE *stream);
   int putchar(int c);

DESCRIPTION

fputc() writes the character c, cast to an unsigned char, to stream.
將指定輸出項 輸出到一個指定流上，包括標準輸出流，標準出錯流，以及任何一個已經成功打開的流(文件)，將轉換爲無符號字符的字符C寫入流

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putc() is equivalent to fputc() except that it may be implemented as a macro which evaluates stream more than once.

將指定輸出項 輸出到一個指定流上，包括標準輸出流，以及任何一個已經成功打開的流(文件)，它可以作爲一個宏來實現

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putchar© is equivalent to putc(c, stdout).
把指定的字符輸出到標準輸出(即終端)

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實驗1 以字符拷貝的方式，fgetc，fputc 實現 cp 命令，mycpy，格式是 ./mycpy srcfile destfile

利用命令行傳參：

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

int main(int argc,char *argv[])
//int main(int argc,char **argv)
{
	FILE *fps=NULL;
FILE *fpd=NULL;
	int ch=0;

//檢查命令行參數
	if(argc < 3)
	{
//向標準錯誤報錯
	fprintf(stderr,"Usage:%s <src_file> <dest_file>\n",argv[0]);
	exit(1);//結束
	}

/* 以只讀的形式打開流
原因1：保證流必須存在，
原因2：不允許改變流 srcfile的內容
*/
	fps = fopen(argv[1],"r");//這裏的argv[1] 即命令行參數中的源文件 srcfile
	if(fps == NULL)
	{
		perror("fopen()");
		exit(1);
	}

	fpd = fopen(argv[2],"w");
	if(fpd == NULL)
	{	
 fclose(fps);//避免內存泄漏
		perror("fopen()");
		exit(1);
	}

	while(1)
	{
		ch = fgetc(fps);
//如果讀到文件尾端或者讀取失敗，退出
		if(ch == EOF)
			break;
 //將讀到的字符寫入目標流
		fputc(ch,fpd);
	}

//先關閉 目的文件，再關閉源文件
	fclose(fpd);
	fclose(fps);
}

mhr@ubuntu:~/work/linux/stdio/mycpy$ gcc mycpy.c 
mhr@ubuntu:~/work/linux/stdio/mycpy$ ll
total 28
drwxrwxr-x 2 mhr mhr 4096 Apr 19 03:36 ./
drwxrwxr-x 3 mhr mhr 4096 Apr 19 03:32 ../
-rwxrwxr-x 1 mhr mhr 8864 Apr 19 03:36 a.out*
-rw-rw-r-- 1 mhr mhr  407 Apr 19 03:34 mycpy.c
-rw-rw-r-- 1 mhr mhr   11 Apr 19 03:36 test1
-rw-rw-r-- 1 mhr mhr    0 Apr 19 03:33 test2
mhr@ubuntu:~/work/linux/stdio/mycpy$ 
mhr@ubuntu:~/work/linux/stdio/mycpy$ ./a.out test1 test2
mhr@ubuntu:~/work/linux/stdio/mycpy$ ll
total 32
drwxrwxr-x 2 mhr mhr 4096 Apr 19 03:36 ./
drwxrwxr-x 3 mhr mhr 4096 Apr 19 03:32 ../
-rwxrwxr-x 1 mhr mhr 8864 Apr 19 03:36 a.out*
-rw-rw-r-- 1 mhr mhr  407 Apr 19 03:34 mycpy.c
-rw-rw-r-- 1 mhr mhr   11 Apr 19 03:36 test1
-rw-rw-r-- 1 mhr mhr   11 Apr 19 03:36 test2
mhr@ubuntu:~/work/linux/stdio/mycpy$ 
mhr@ubuntu:~/work/linux/stdio/mycpy$ diff test1 test2
mhr@ubuntu:~/work/linux/stdio/mycpy$ 
mhr@ubuntu:~/work/linux/stdio/mycpy$ ./a.out 
Usage:./a.out <src_file> <dest_file>
mhr@ubuntu:~/work/linux/stdio/mycpy$ 

可以查看 讀出來或者寫進去的 ch值，即

printf("write char character = %d\n",ch);
或
printf("write char character = %c\n",ch);

mhr@ubuntu:~/work/linux/stdio/mycpy$ gcc mycpy.c 
mhr@ubuntu:~/work/linux/stdio/mycpy$ ./a.out test1 test2
write char character = 48
write char character = 49
write char character = 50
write char character = 51
write char character = 52
write char character = 53
write char character = 54
write char character = 55
write char character = 56
write char character = 57
write char character = 10
mhr@ubuntu:~/work/linux/stdio/mycpy$ 
mhr@ubuntu:~/work/linux/stdio/mycpy$ gcc mycpy.c 
mhr@ubuntu:~/work/linux/stdio/mycpy$ ./a.out test1 test2
write char character = 0
write char character = 1
write char character = 2
write char character = 3
write char character = 4
write char character = 5
write char character = 6
write char character = 7
write char character = 8
write char character = 9
write char character = 

mhr@ubuntu:~/work/linux/stdio/mycpy$ 

實驗2 利用 fgetc()查看一個文件中有多少個有效字符

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

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

//此時實驗是小文件，用int 計算文件中字符個數不會溢出。如果是大文件 可以用long
	int count = 0;

	if(argc < 2)
	{
	fprintf(stderr,"Usage:%s <src_file> <dest_file>\n",argv[0]);
	exit(1);
	}
	
	fp = fopen(argv[1],"r");
	if(fp == NULL)
	{
		perror("fopen()");
		exit(1);
	}
	
//如果讀到文件尾
	while(fgetc(fp) != EOF)
	{
		count ++;
	}

	printf("count = %d\n",count);
	fclose(fp);
	exit(0);
}

mhr@ubuntu:~/work/linux/stdio$ ll
total 44
drwxrwxr-x 3 mhr mhr 4096 Apr 19 03:57 ./
drwxrwxr-x 3 mhr mhr 4096 Apr 16 08:28 ../
-rwxrwxr-x 1 mhr mhr 8936 Apr 19 03:57 a.out*
-rw-rw-r-- 1 mhr mhr  376 Apr 19 03:57 fgetc.c
-rw-rw-r-- 1 mhr mhr   11 Apr 19 03:54 test
mhr@ubuntu:~/work/linux/stdio$ 
mhr@ubuntu:~/work/linux/stdio$ gcc fgetc.c 
mhr@ubuntu:~/work/linux/stdio$ ./a.out test 
count = 11
mhr@ubuntu:~/work/linux/stdio$