c - 按 ID 在文本文件中搜索名称
问题描述
我有一个包含 2 行的文本文件:
Voicu;卡塔林;1234;2.32
戴安娜;卡达尔;2345;1.01
我试图让我的程序在 .txt 文件中搜索 ID(1234 或 2345)并将其与名称匹配。下面是我尝试制作的代码,但是在我在第一个scanf中写入后它不会在.txt中找到ID,出现的第一件事是“else”行。
void alegereStudent(struct student *stud)
{
FILE *scStudenti = fopen("studenti.txt", "a");
char *error;
int i=0,n;
if(scStudenti==NULL)
{
error = strerror(errno);
printf("Fisierul nu poate fi creat: \n %s", error);
}
printf("\nIntroduceti Numele: ");
scanf("%39s", stud->numeStudent);
printf("Introduceti Prenumele: ");
scanf("%39s", stud->prenumeStudent);
printf("Introduceti ID-ul studentului: ");
scanf("%d", &stud->idStudent);
printf("Introduceti Media de admitere: ");
scanf("%f", &stud->medieAdmitere);
fprintf(scStudenti,"<%s>;", stud->numeStudent);
fprintf(scStudenti,"<%s>;", stud->prenumeStudent);
fprintf(scStudenti,"<%d>;", stud->idStudent);
fprintf(scStudenti,"<%.2f>\n", stud->medieAdmitere);
fclose(scStudenti);
}
//
void optiunea_2()
{
printf("\n1.Despre studenti.\n");
printf("2.Despre profesori.\n");
printf("3.Revenire la meniu principal.\n");
printf("\nAlegeti o optiune: ");
scanf("%d",&alegere_opt2);
switch(alegere_opt2)
{
case 1: while(&stud!=NULL)
{
FILE *scStudenti = fopen("studenti.txt", "r");
char *error;
int cautareID;
if(scStudenti==NULL)
{
error = strerror(errno);
printf("Fisierul nu poate fi creat: \n %s", error);
}
printf("\nIntroduceti ID-ul studentului: ");
scanf("%d", &cautareID);
fscanf(scStudenti,"%d",&stud->idStudent);
if(cautareID==&stud->idStudent)
{
printf("Numele Studentului este %s %s",&stud->numeStudent, &stud->prenumeStudent);
}
else
printf("\nAcest ID nu exista!\n");
optiunea_2();
}break;
解决方案
fprintf(scStudenti,"<%s>;", stud->numeStudent); fprintf(scStudenti,"<%s>;", stud->prenumeStudent); fprintf(scStudenti,"<%d>;", stud->idStudent); fprintf(scStudenti,"<%.2f>\n", stud->medieAdmitere); fclose(scStudenti);
This makes formatting much more difficult. The output file will contain:
<first>;<last>;<1234>;<0.5>
You want to start with a new file and simplify the output to write:
first;last;1234;0.5
Don't always put &
in front of integer. Just use:
if(cautareID == stud->idStudent)
{
...
}
Example:
const char *filename = "studenti.txt";
void alegereStudent()
{
struct student stud;
FILE *scStudenti = fopen(filename, "a");
if(scStudenti == NULL)
{
printf("error\n");
return;
}
printf("\nIntroduceti Numele: ");
scanf("%39s", stud.numeStudent);
printf("Introduceti Prenumele: ");
scanf("%39s", stud.prenumeStudent);
printf("Introduceti ID-ul studentului: ");
scanf("%d", &stud.idStudent);
printf("Introduceti Media de admitere: ");
scanf("%f", &stud.medieAdmitere);
fprintf(scStudenti, "%s;", stud.numeStudent);
fprintf(scStudenti, "%s;", stud.prenumeStudent);
fprintf(scStudenti, "%d;", stud.idStudent);
fprintf(scStudenti, "%.2f\n", stud.medieAdmitere);
fclose(scStudenti);
}
void find_by_id(int id)
{
FILE *fin = fopen(filename, "r");
if(!fin)
return;
int count = 0;
struct student stud;
while(fscanf(fin, "%39[^;];%39[^;];%d;%f\n",
stud.numeStudent, stud.prenumeStudent, &stud.idStudent, &stud.medieAdmitere) == 4)
{
if(id == stud.idStudent)
{
printf("found %s %s\n", stud.numeStudent, stud.prenumeStudent);
}
count++;
}
if(count == 0)
printf("failed to read any record. Start with a new file.\n");
}
int main(void)
{
alegereStudent();
find_by_id(1234);
return 0;
}
If <>
characters are added, then read according to that format, you then have to remove the extra <>
characters from the string.
void alegereStudent()
{
struct student stud;
...
fprintf(scStudenti, "<%s>;", stud.numeStudent);
fprintf(scStudenti, "<%s>;", stud.prenumeStudent);
fprintf(scStudenti, "<%d>;", stud.idStudent);
fprintf(scStudenti, "<%.2f>\n", stud.medieAdmitere);
fclose(scStudenti);
}
void find_by_id(int id)
{
...
struct student stud;
while(fscanf(fin, "%39[^;];%39[^;];<%d>;<%f>\n",
stud.numeStudent, stud.prenumeStudent, &stud.idStudent, &stud.medieAdmitere) == 4)
{
if(id == stud.idStudent)
{
char *p;
size_t i;
//remove the extra <> characters
p = stud.numeStudent;
if (strlen(p) > 1)
{
for(i = 1; i < strlen(p) - 1; i++)
p[i - 1] = p[i];
p[i - 1] = 0;
}
//remove the extra <> characters
p = stud.prenumeStudent;
if (strlen(p) > 1)
{
for(i = 1; i < strlen(p) - 1; i++)
p[i - 1] = p[i];
p[i - 1] = 0;
}
printf("found %s %s\n", stud.numeStudent, stud.prenumeStudent);
}
count++;
}
if(count == 0)
printf("failed to read any record. Start with a new file.\n");
}
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