题目：

修改下列程序，用命令行界面代替交互式界面

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define BUFSIZE 4096

#define SLEN 81

void append(FILE * source,FILE * dest);

char * s_gets(char * st,int n);

int main(){

FILE * fa, * fs;

int files = 0;

char file_app[SLEN];

char file_src[SLEN];

int ch;

puts("Enter name of destination file: ");

s_gets(file_app,SLEN); //输入目标文件名

if((fa = fopen(file_app,"a+")) == NULL){

fprintf(stderr,"cant't open %s\n",file_app);

exit(EXIT_FAILURE);

}

if(setvbuf(fa,NULL,_IOFBF,BUFSIZE) != 0){

fputs("Can't create output buffer\n",stderr);

exit(EXIT_FAILURE);

}

puts("Enter name of first source file (empty line to quit): ");

while(s_gets(file_src,SLEN) && file_src[0] != '\0'){

if(strcmp(file_src,file_app) == 0) fputs("Can't append file to itself\n",stderr);

else if((fs = fopen(file_src,"r")) == NULL) fprintf(stderr,"Can't open %s\n",file_src);

else{

if(setvbuf(fs,NULL,_IOFBF,BUFSIZE) != 0){

fputs("Cant's append file to itself\n",stderr);

continue;

}

append(fs,fa);

if(ferror(fs) != 0) fprintf(stderr,"Error in reading file %s.\n",file_src);

if(ferror(fa) != 0) fprintf(stderr,"Error in writing file %s.\n",file_app);

fclose(fs); //关闭读取文件，继续下一次的读取

files++;

printf("File %s appended.\n",file_src);

puts("Next file (empty line to quit): ");

}

}

printf("Done appending. %d files appended.\n",files);

rewind(fa);

printf("%s contents:\n",file_app);

while((ch = getc(fa)) != EOF) putchar(ch);

puts("Done displaying.");

fclose(fa);

return 0;

}

void append(FILE * source,FILE * dest){

size_t bytes;

static char temp[BUFSIZE];

while(( bytes = fread(temp,sizeof(char),BUFSIZE,source)) > 0){

fwrite(temp,sizeof(char),bytes,dest);

}

}

char * s_gets(char * st,int n){

char * ret_val;

char * find;

ret_val = fgets(st,n,stdin);

if(ret_val){

find = strchr(st,'\n');

if(find) *find = '\0';

else{

while(getchar() != '\n')

continue;

}

}

}

源代码：

#include <stdio.h> #include <stdlib.h> #include <string.h> #define BUFSIZE 4096 #define SLEN 81 void append(FILE * source,FILE * dest); char * s_gets(char * st,int n); int main(int argc,char * argv[]){ FILE * fa, * fs; int files = 0; int ch; if((fa = fopen(argv[1],"a+")) == NULL){ fprintf(stderr,"cant't open %s\n",argv[1]); exit(EXIT_FAILURE); } if(setvbuf(fa,NULL,_IOFBF,BUFSIZE) != 0){ fputs("Can't create output buffer\n",stderr); exit(EXIT_FAILURE); } for(int i = 2;i <= argc-1;i++){ if(strcmp(argv[i],argv[1]) == 0) fputs("Can't append file to itself\n",stderr); else if((fs = fopen(argv[i],"r")) == NULL) fprintf(stderr,"Can't open %s\n",argv[i]); else{ if(setvbuf(fs,NULL,_IOFBF,BUFSIZE) != 0){ fputs("Cant's append file to itself\n",stderr); continue; } append(fs,fa); if(ferror(fs) != 0) fprintf(stderr,"Error in reading file %s.\n",argv[i]); if(ferror(fa) != 0) fprintf(stderr,"Error in writing file %s.\n",argv[1]); fclose(fs); //关闭读取文件，继续下一次的读取 files++; printf("File %s appended.\n",argv[i]); } } printf("Done appending. %d files appended.\n",files); rewind(fa); printf("%s contents:\n",argv[1]); while((ch = getc(fa)) != EOF) putchar(ch); puts("\nDone displaying."); fclose(fa); return 0; } void append(FILE * source,FILE * dest){ size_t bytes; static char temp[BUFSIZE]; while(( bytes = fread(temp,sizeof(char),BUFSIZE,source)) > 0){ fwrite(temp,sizeof(char),bytes,dest); } } char * s_gets(char * st,int n){ char * ret_val; char * find; ret_val = fgets(st,n,stdin); if(ret_val){ find = strchr(st,'\n'); if(find) *find = '\0'; else{ while(getchar() != '\n') continue; } } }

演示效果：

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