Read data to Text File and reserve de output with N character - c

Question

I want read data from console and output to Text file with reserve of N character per variable of structure type.
The Text file is similar to:
1 111 1 Peter
22 22 2 John Lays
3 3 3 Anne Belgs
I do not know if I'm using the most correct functions.
Also I can not read ("carro.name") more than 1 word (example: John Lays)
struct estruturaCarro {
int id, potencia, avariado;
char name[11];
} carro;
...
//Read data to Text File:
...
printf("\n ID......:"); scanf("%d", &carro.id);
printf("\n Potencia:"); scanf("%d", &carro.potencia);
printf("\n Avariado:"); scanf("%d", &carro.avariado);
printf("\n NAME:"); scanf("%10[0-9a-zA-Z ]", carro.name); // or scanf("%[^\n]s",...)
fprintf(fp, "%-2d %-3d %-1d %-10s \n\n", carro.id, carro.potencia, carro.avariado, carro.name);
...
//Show File Text data:
...
int registos=0;
while(1)
{
fscanf(fp, "%d %d %d %-10s", &carro.id, &carro.potencia, &carro.avariado, carro.name);
if(feof(fp)){ break; }
printf("%-2d %-3d %-1d %-10s\n", carro.id, carro.potencia, carro.avariado, carro.name);
registos++;
}
printf("\nCarros=%d", registos);

Answer 1

As you say in your question you cannot use scanf to read a complex name including spaces.
But before to search how to do it is needed to decide what to do.
Probably you do not want to memorize the extra spaces at the beginning and at the end (including the newline), and probably a name must not be empty.
But what about inside a complex name ? If the user enter John Lays do you save the name with the two spaces or you want to simplify to have only one ? Do you have to manage other special character like '-' (are John - Lays / John- Lays / John -Lays read as John-Lays ?).
What to do if the input string is longer than 10 characters ? Just to stop to read letting the rest for the next read or to bypass up to a newline ? Because you print a message before each input you clearly want an input per line and the rest of the line must be bypassed.
If you do not want to read the string as it is enter the best way is probably to write your own read string function.
You also have to decide what to do if the user do not enter a number for ID or Potencia or Avariado, currently you do not even detect the error, this is not a good way. So in that case do you abort all (exit program), or you redo the read ? Probably you prefer to read again, for that you need to bypass the invalid input, but what that means, to bypass all up to a newline ?
For instance :
#include <stdio.h>
#include <string.h>
#include <ctype.h>
/* read an int memorizing its value in v,
return 0 in case of EOF else a non null value */
int readInt(const char * msg, int * v)
{
for (;;) {
fputs(msg, stdout);
if (scanf("%d", v) == 1)
return 1;
/* not a number or EOF, bypass all up to \n */
int c;
while ((c = fgetc(stdin)) != '\n')
if (c == EOF)
return 0;
puts("invalid value"); /* message may be also get in argument */
}
}
/* read a string up to a \n
remove extra spaces at the beginning and end
simplify internal multiple spaces
accept any character and do not manage in a special way characters like like '-'
a non empty string must be read
read at most sz-1 characters in s then place the null character (as fgets), sz must be > 1
if the line too long bypass the rest of the input up to \n
return 0 in case of EOF else a non null value */
int readStr(const char * msg, char * s, size_t sz)
{
fputs(msg, stdout);
/* read the first char bypassing spaces including \n */
if (scanf(" %c", s) == 0)
// EOF
return 0;
size_t index = 1;
int c;
sz -= 1;
while (index != sz) {
c = fgetc(stdin);
if ((c == EOF) || (c == '\n'))
break;
if (!isspace(c))
s[index++] = c;
else if (s[index - 1] != ' ')
s[index++] = ' ';
}
s[(s[index - 1] != ' ') ? index : index-1] = 0;
// bypass possible rest of the line
while ((c != EOF) && (c != '\n'))
c = fgetc(stdin);
return 1;
}
/* ******************* */
struct estruturaCarro {
int id, potencia, avariado;
char name[11];
} carro;
int main()
{
do {
if (!readInt("\n ID......:", &carro.id) ||
!readInt("\n Potencia:", &carro.potencia) ||
!readInt("\n Avariado:", &carro.avariado) ||
!readStr("\n NAME:", carro.name, sizeof(carro.name))) {
puts("EOF");
return -1;
}
else
printf("%-2d %-3d %-1d '%-10s' \n\n", carro.id, carro.potencia, carro.avariado, carro.name);
} while (strcmp(carro.name, "end"));
return 0;
}
Compilation and execution:
pi#raspberrypi:/tmp $ gcc -pedantic -Wextra -Wall r.c
pi#raspberrypi:/tmp $ ./a.out
ID......:aze
invalid value
ID......:qsd
invalid value
ID......:1
Potencia:2
Avariado:3
NAME:aze u iiiiiiiiiiiiiiiiii
1 2 3 'aze u iiii'
ID......:11
Potencia:22
Avariado:0
NAME: end
11 22 0 'end '
pi#raspberrypi:/tmp $
When you read in your file and supposing it was produced doing fprintf(fp, "%-2d %-3d %-1d %-10s", ...) :
char line[21]; /* each line has 20 characters newline included */
while (fgets(line, sizeof(line), fp) != NULL) {
if (sscanf(line, "%d %d %d", &carro.id, &carro.potencia, &carro.avariado) != 3)
/* abnormal case, invalid file */
break; /* anything else you want to do */
/* the string starts at the index 9 and has 10 characters out of the newline */
memcpy(carro.name, line + 9, 10);
carro.name[10] = 0;
/* ... */
}
note the name have spaces at the end if its length is less than 10 characters
Or you can read in a way similar to the previous on stdin.