C language-weird output using fgets - c

Question

here's the code in question:
FILE *fp;
char str[256];
/* opening file for reading */
fp = fopen("file.txt" , "r");
if(fp == NULL) {
perror("Error opening file");
return(-1);
}
while( fgets (str, sizeof(str), fp)) {
int i;
char *temp;
temp=malloc(257);
for(i=0;i<sizeof(str)-1;i++){
if(isalpha(str[i])){
append(temp,str[i]);
}else{
printf(" %s ",temp);
temp=calloc(257,sizeof(char));
}
}
}
if the text file is the following:
"Here's a text
file example. No
idea what's wrong."
then it will output the following:
"Here s a text vf file example No vf idea what s wrong".
Desired output for reference:
"Here s a text file example No idea what s wrong"
Basically some weird stuff every time there's a newline involved. Could be "vf" when i run it. Could be "ZG" the next time. It changes every time i run the program.

Answer 1

Reading parts of buf not filled by fgets()`.
Replace
// for(i=0;i<sizeof(str)-1;i++)
for(i=0;i<strlen(str);i++)
or better
// for(i=0;i<sizeof(str)-1;i++)
size_t len = strlen(str);
// removed potenital ending '\n'
if ((len > 0) && (str[len-1] == '\n')) len--;
size_t i;
for (i = 0; i < len; i++)

Answer 2

Perhaps I didn't understand what you're doing but if you just want to read the whole file in one string you can do something like this
int main(int argc, const char * argv[])
{
FILE *fp;
char str[256];
char *temp = calloc(257, 1);
fp = fopen("file.txt" , "r");
if(fp == NULL) {
perror("Error opening file");
return(-1);
}
while( fgets (str, sizeof(str), fp)) {
int i;
//char *temp;
if (str[strlen(str)-1] == '\n') {
str[strlen(str)-1] = ' ';
}
strncat(temp, str, 257);
}
puts(temp);
}
There is no problem with fgets. It automatically appends terminating null character.
Also you do not free memory before allocating new. It's not good.

Answer 3

#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *fp;
char str[256];
/* opening file for reading */
fp = fopen("file.txt" , "r");
if(fp == NULL) {
perror("Error opening file");
return(-1);
}
while( fgets (str, sizeof(str), fp)) {
int i;
char temp[256]; //buffer; can allocate on the stack, no need for malloc
char *temp1; //pointer at the beginning of the buffer (used to do my own append())
temp1=temp; //for my own appending
for(i=0;i<sizeof(str);i++){
int ch=str[i]; //alias the str[i]
if(isalpha(ch)||ch=='"'){ //let these chars thru
*temp1++=ch; //my own append()
}else if(ch=='\0'){//already at the end of buffer, end loop and print
*temp1=ch; //don't forget to end the string with '\0' (for printing functions)
break;
}else if(ch=='.'){ // you seem to want to skip dots
continue;
}
else {
*temp1++=' '; //replace other nonalpha characters with ' '
}
}
printf("%s",temp);
}
}