K& R2，练习7.6

目的::参见评论中的陈述


GOT：分段错误


我猜这段错误来自编译时警告但我已经

已经为这个功能提供了一个char *。


/ * K& R2，7.7节，练习7.6 >
*

*写一个程序来比较2个文件，打印第一行

*它们不同的地方。

*

* /

#include< stdio.h>

#include< stdlib.h>

＃ include< string.h>


enum MAXSIZE {ARRSIZE = 1000};


void compare_files（FILE *，FILE *）;

void print_line（char *）;

int main（int argc，char * argv []）

{

FILE * pf1，* pf2;


if（argc！= 3）

{

fprintf（stderr，"你iDiOT，我希望2个文件作为输入。\ n"）;

退出（EXIT_FAILURE）;

}

/ *打开文件* /

pf1 = fo笔（* ++ argv，" r" ）;

pf2 = fopen（* ++ argv，" r"）;


/ *错误检查* /

if（pf1 == NULL || pf2 == NULL）

{

fprintf（stderr，错误打开文件\ n）;

退出（EXIT_FAILURE）;

}

其他

{

compare_files（pf1，pf2） ;

}


/ *别忘了关闭文件* /

fclose（pf1）;

fclose（pf2）;

返回0;

}


/ *比较2个文件* /

void compare_files（FILE * pf1，FILE * pf2）

{

int c1，c2，match;

char * line1，* line2;

char * begin_line1，* begin_line2;


match = 1;


while（（（line1 = fgets（line1，ARRSIZE，pf1））！= NULL）||

（（line2 = fgets（line2，ARRSIZE，pf2））！= NULL））

{

begin_line1 = line1;

begin_line2 = line2;


for（c1 = * line1， c2 = * line2; c1！=' '\ 0''&& c2！=''\'''; ++ line1，

++ line2）

{

if（c1！= c2）

{

match = 0;

print_line（begin_line1）;

printf（" \\\
----------- ------------ \\\
&QUOT）; print_line（begin_line2）;

}

}

}

}


void print_line（char * line）

{

printf（"％s \ n"，* line ++）;

}


==================输出================== ====

[arnuld @ raj C] $ gcc -ansi -pedantic -Wall -Wextra 7-6.c

7-6.c：in function` print_line''：

7-6.c：88：警告：格式参数不是指针（arg 2）


[arnuld @ raj C] $ ./a.out

你iDiOT，我希望2个文件作为输入。


[arnuld @ raj C] $ ./a.out 7- 6.c 5-4.c

分段错误

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PURPOSE :: see statement in comments

GOT: Segmentation Fault

I guess the segfault is sourced in the compile-time warning but I am
giving a char* to the function already.


/* K&R2, section 7.7, exercise 7.6
*
* write a program to compare 2 files, printing that first line
* where they differ.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum MAXSIZE { ARRSIZE=1000 };

void compare_files( FILE*, FILE* );
void print_line( char* );
int main( int argc, char* argv[] )
{
FILE *pf1, *pf2;

if( argc !=3 )
{
fprintf( stderr, "You iDiOT, I expect 2 files as input. \n" );
exit(EXIT_FAILURE);
}
/* open files */
pf1 = fopen( *++argv, "r" );
pf2 = fopen( *++argv, "r" );

/* error check */
if( pf1 == NULL || pf2 == NULL )
{
fprintf( stderr, "error opening files\n");
exit(EXIT_FAILURE);
}
else
{
compare_files( pf1,pf2 );
}

/* don''t forget to close the files */
fclose( pf1 );
fclose( pf2 );
return 0;
}

/* compare 2 files */
void compare_files( FILE* pf1, FILE* pf2 )
{
int c1, c2, match;
char *line1, *line2;
char *begin_line1, *begin_line2;

match = 1;

while( ((line1 = fgets( line1, ARRSIZE, pf1 )) != NULL) ||
((line2 = fgets( line2, ARRSIZE, pf2 )) != NULL))
{
begin_line1 = line1;
begin_line2 = line2;

for( c1 = *line1, c2 = *line2; c1 != ''\0'' && c2 != ''\0''; ++line1,
++line2 )
{
if ( c1 != c2 )
{
match = 0;
print_line( begin_line1 );
printf("\n-----------------------\n"); print_line( begin_line2 );
}
}
}
}

void print_line( char* line )
{
printf("%s\n", *line++);
}

================== OUTPUT ======================
[arnuld@raj C]$ gcc -ansi -pedantic -Wall -Wextra 7-6.c
7-6.c: In function `print_line'':
7-6.c:88: warning: format argument is not a pointer (arg 2)

[arnuld@raj C]$ ./a.out
You iDiOT, I expect 2 files as input.

[arnuld@raj C]$ ./a.out 7-6.c 5-4.c
Segmentation fault
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