文件读写到同一个文件? [英] File read write to same file?
问题描述
我已经成功地打开文件和读取,而以 VAR =的fopen写入到另一个文件(文件,R)
/ W
但即使R +或W + moded我无法打开的文件,并修改其内容。
I've managed to open a file and read while writing to another file with var=fopen(file,"r")
/ "w"
but even with r+ or w+ moded I can't open a file and alter its contents.
想象一下:
int formatacao (char original[]){/*se a cadeia nao tiver escrita em maiusculas, esta funçao vai alteralas para tal*/
int val1;
FILE * original_open;
original_open = fopen (original,"r+");
if (original_open==0){
printf ("ficheiro %c 1.",original);
}
while ((val1=fgetc(original_open))!=EOF){
if (val1>='a'&&val1<='z'&&val1){
fputc(val1-32,original_open);
}
else
fputc(val1,original_open);
}
fclose (original_open);
return (0);
}
code ++工程,没有错误,没有警告,唯一的问题是:它删除该文件的内容,如果我使用它像这一点,但这个作品:
Code works, no errors, no warning, only problem is: it erases the contents on the file if I use it like this BUT this works:
int main (){
int val1,val2,nr=0;
FILE* fp1;
FILE* fp2;
fp1=fopen ("DNAexample.txt","r");
fp2=fopen ("DNAexample1.txt","w");
if (fp1==0){
printf ("EPIC FAIL no 1.\n");
}
while ((val1=fgetc(fp1))!=EOF){
if (val1>='a'&&val1<='z'&&val1){
fputc(val1-32,fp2);
}
else
fputc(val1,fp2);
}
fclose (fp1);
fclose (fp2);
return (0);
}
完美地!我怎么能打开一个文件,通过炭炭阅读并决定,如果我想改变char或不?
Flawlessly! How can I open a file, read char by char and decide if I want to change the char or not?
推荐答案
您需要进行干预,输出和输入之间的文件定位功能,除非EOF于输入中找到。
You need to intervene a file positioning function between output and input unless EOF was found on input.
这对我的作品:
#include <stdio.h>
int formatacao (char *original) {
int val1;
FILE *original_open;
int write_at, read_at;
original_open = fopen(original, "r+");
if (original_open == 0) {
printf("ficheiro %s\n", original);
}
write_at = read_at = 0;
while ((val1 = fgetc(original_open)) != EOF) {
read_at = ftell(original_open);
fseek(original_open, write_at, SEEK_SET);
if (('a' <= val1) && (val1 <= 'z')) {
fputc(val1 - 32, original_open);
} else {
fputc(val1, original_open);
}
write_at = ftell(original_open);
fseek(original_open, read_at, SEEK_SET);
}
fclose(original_open);
return (0);
}
int main(void) {
formatacao("5787867.txt");
return 0;
}
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