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[英]How can I scan a file for a word and then print the line containing that word in another file in C programming?
[英]Scan each word or number in line and print to file using C
我在data1.txt文件中有2行(如下所示):
Da KOL -1.19503 5.27557163
MaB KOL -1.19503 5.27557163
我不確定如何使用fgets
提取特定的單詞或數字,因此我使用fscanf
掃描集合的每個組成部分並將它們打印到另一個文件中。 代碼是:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<ctype.h>
#include<math.h>
main()
{
FILE *fpt1, *fpt2;
fpt1=fopen("data1.txt","r");
fpt2=fopen("data2.txt","w");
int i;
double ep, si;
char *sto1, *sto2;
for(i=0;i<2;i++)
{
fscanf(fpt1,"%s\n",sto1);
fscanf(fpt1,"%s\n",sto2);
fscanf(fpt1,"%lf\n",&ep);
fscanf(fpt1,"%lf\n",&si);
fprintf(fpt2,"%s %s %2.8lf %2.8lf\n",sto1,sto2,ep,si);
}
fclose(fpt1);
fclose(fpt2);
}
但我在文件data2.txt中得到此輸出:
Da (null) 0.00000000 0.00000000
KOL (null) -1.19503000 5.27557163
雖然,所需的輸出是一行的每個部分之間有一個空格的輸出,例如:
Da KOL -1.19503 5.27557163
MaB KOL -1.19503 5.27557163
有人可以幫我解決這個問題嗎?
#include <stdio.h>
//A good habit is not to use "main()"
int main(int argc, char *argv[])
{
FILE *fpt1, *fpt2;
fpt1=fopen("data1.txt","r");
fpt2=fopen("data2.txt","w");
int i;
double ep, si;
char sto1[100], sto2[100]; //here neeed array
for(i=0;i<2;i++)
{
fscanf(fpt1,"%s",sto1); //without '\n'
fscanf(fpt1,"%s",sto2);
fscanf(fpt1,"%lf",&ep);
fscanf(fpt1,"%lf",&si);
fprintf(fpt2,"%s %s %2.8lf %2.8lf\n",sto1,sto2,ep,si);
}
fclose(fpt1);
fclose(fpt2);
return 0;
}
您的想法是正確的,但我已經對您的代碼進行了一些修改/更正。 而且我用sscanf
代替了fscanf
。 這是代碼,
#include<stdio.h>
#define MAX 256
int main(){
FILE *pfile1 =NULL,*pfile2 = NULL;
char *sto1=NULL,*sto2=NULL,line[MAX];
double ep,si;
pfile1 = fopen("dS.txt","r");
pfile2 = fopen("dR.txt","w");
if(pfile1 != NULL || pfile2 != NULL){
while(fgets(line,255,pfile1)!=NULL){
sscanf(line,"%s %s %Lf %Lf",&sto1,&sto2,&ep,&si);
fprintf(pfile2,"%s %s %2.5Lf %2.8Lf\n",&sto1,&sto2,ep,si);
}
fclose(pfile1);
fclose(pfile2);
}
return 0;
}
您使用了具有自動存儲持續時間sto1
和sto2
的未初始化變量的值,並調用了未定義的行為 。
在使用指向有效緩沖區的指針之前,請為其分配指針。
#include<stdio.h>
#include<stdlib.h>
int main(void)
{
FILE *fpt1, *fpt2;
fpt1=fopen("data1.txt","r");
fpt2=fopen("data2.txt","w");
int i;
double ep, si;
char *sto1, *sto2;
/* allocate enough size to store data */
sto1 = malloc(1000000);
sto2 = malloc(1000000);
for(i=0;i<2;i++)
{
fscanf(fpt1,"%s\n",sto1);
fscanf(fpt1,"%s\n",sto2);
fscanf(fpt1,"%lf\n",&ep);
fscanf(fpt1,"%lf\n",&si);
fprintf(fpt2,"%s %s %2.8lf %2.8lf\n",sto1,sto2,ep,si);
}
fclose(fpt1);
fclose(fpt2);
free(sto1);
free(sto2);
}
為fopen()
, malloc()
和fscanf()
添加錯誤檢查將使此代碼更好。
另一種方法是使用靜態分配的數組,而不是通過內存管理功能動態分配緩沖區。
#include<stdio.h>
int main(void)
{
FILE *fpt1, *fpt2;
fpt1=fopen("data1.txt","r");
fpt2=fopen("data2.txt","w");
int i;
double ep, si;
char sto1[1000], sto2[1000]; /* allocating too big array as automatic local variable may cause stack overflow */
for(i=0;i<2;i++)
{
fscanf(fpt1,"%s\n",sto1);
fscanf(fpt1,"%s\n",sto2);
fscanf(fpt1,"%lf\n",&ep);
fscanf(fpt1,"%lf\n",&si);
fprintf(fpt2,"%s %s %2.8lf %2.8lf\n",sto1,sto2,ep,si);
}
fclose(fpt1);
fclose(fpt2);
}
您可以使用靜態數組
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