用户输入一个文本名，编程实现输出文本中最长的一行。如果最长的不止一行，请全部输出。
程序如下:
#include<stdio.h>
int main(int a, char * arg[])
{
char file_name[31];
FILE * file;
long lines[20]; /* store the offset */
unsigned int length = 0; /* length of the line */
unsigned int num = 0; /* number of lines */
char buf[200];
char c;
unsigned int n = 0;
/* Get the file name, and print the name to the screen. */
if( a == 2 ){
strcpy(file_name,arg[1]);
}
else{
printf(“\nPlease enter a file name:”);
scanf(“%s”,file_name);
}
printf(“The file name is: %s\n”,file_name);
/* Open the file, the program will be stop if it failed. */
file = fopen(file_name,”r”);
if( file==NULL ){
printf(“No such file!\n”);
return 0;
}
/* Fined out the lengthest line. */
do{
c = fgetc( file );
n++;
if( c==’\n’ ){
if( n>length ){
lines[0] = ftell(file)-n-1;
num = 1;
length = n;
}
else if( n==length ){
lines[num] = ftell(file)-n-1;
num++;
}
else ;
n = 0;
}
}while(c!=EOF);
n = n;
/* Print. */
printf(“The longest lines of the file is:\n”);
while( 0 != num– ){
fseek( file,lines[num],SEEK_SET );
fgets( buf,length,file );
printf(“%s\n”,buf );
}
}
BUG肯定有，主要就是缓冲区溢出。分数应该会得。该程序可以用命令行方式输入文件名参数。
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