** 26/10更新 - >首先感谢大家的帮助,我现在越来越近了,我需要更多的工作和学习,但我真的很感谢你帮助了我很多:-)
仍然不知道为什么input.txt文件中的第一个“rain”字没有得到strcmp的正输出,而且从cmd我可以看到“<”括号不会出现,除了最后一行,这是有效的线。
还检查了Removing trailing newline character from fgets() input的突出显示的回复
即使我将代码更改为以下内容:
while( fgets (line, sizeof line, fp)!=NULL ) {
/* remove \n from at the end of the str buffer*/
char * pos;
/*
if ((pos = strchr(line, '\n')) != NULL)
*pos = '\0';
*/
line[strcspn(line, "\n")] = 0;
我得到的结果与我使用if块的结果相同。也许我会得到额外的\ 0可能是这种情况。任何人都有一个链接,我可以阅读我刚才使用的分隔符,或者调试器的一个很好的参考等等......我一看到这个就会看看它?非常感谢你提前!
read5.c版本:现在从那个input.txt文件,它在最后一个“rain”字上有一个额外的空格,我删除了空格,它能够找到并得到最后一个字比较作为一个真实的结果,运行strcmp if块。但那是唯一一个字符串,它是if if block的真正积极结果。
在cmd我可以看到:
$./read5 input.txt rain output.txt sun
>Maria
>rain
>manel
>Bla bla
<rain>
Found it! rain
在output.txt上它变成:
Maria
rain
manel
Bla bla
sun
read5.c
#include <stdio.h>
#include <string.h>
/**
* Compile program:
* gcc read3.c -o read3
*
*/
int main (int argc, char **argv) {
FILE *fp, *fo;
char *compare, *replace;
char line[246];
if (argc <= 4){
printf(">Missing arguments on the command line.\n");
printf(">Be sure you run the program as\n\"./read3 input.txt compare outout.txt replace\"\n\n");
}
/* opening file for reading */
fp = fopen(argv[1] , "r");
if(fp == NULL){
perror("Error opening input file");
return 1;
}
compare = argv[2];
fo = fopen(argv[3], "w");
if(fo == NULL){
perror("Error opening output file");
return 1; //TODO check if: return 1 because it was expected, right?
}
replace = argv[4];
/*
printf(); made to test version 2
//printf("We are going to compare %s\n", compare);
//printf("We are going to replace it with %s\n", replace);
*/
while( fgets (line, sizeof line, fp)!=NULL ) {
/* remove \n from at the end of the str buffer*/
char * pos;
if ((pos = strchr(line, '\n')) != NULL)
*pos = '\0';
/* print str enclosed in <> so we can see what str actually contains */
//printf("Inside the loop, got the string: %s\n", line);
//printing the strings with defined delimiters
printf("<%s>\n", line);
if(strcmp(compare, line) == 0){
printf("Found it! %s \n", line);
fprintf(fo, "%s\n", replace);
}
else{
fprintf(fo, "%s\n", line);
}
}
fclose(fp);
fclose(fo);
return 0;
}
没有编辑的第一个问题:25/10
我需要制作一个像这样运行的程序:
./read2 input.txt rain output.txt sun
它读取input.txt
,搜索rain
字符串,如果找到它,用sun
字符串替换它,并输出input.txt
的所有文本与output.txt
的替换。
但是到目前为止我使用的代码,strcmp
并没有比较我想要的字符串,也许它在命令行上有额外的空间,我不知道......现在正在做的是复制一切从input.txt
到output.txt
...它总是运行else
块...
Read2.c:
#include <stdio.h>
#include <string.h>
int main(int argc, char **argv) {
FILE *fp, *fo;
char str[60];
//char* token;
/* opening file for reading */
fp = fopen(argv[1], "r");
char *compare = argv[2];
fo = fopen(argv[3], "w+");
char *replace = argv[4];
if (fp == NULL) {
perror("Error opening file");
return(-1);
}
//printf("We are going to compare %s\n", compare);
//printf("We are going to replace it with %s\n", replace);
while (fgets(str, 60, fp) != NULL) {
/* writing content to stdout */
//Take the \n out
//token = strtok(str, "\n");
printf("Inside the loop, got the string: %s\n", str);
if (strcmp(compare, str) == 0) {
//puts(str);
printf("Found it! %s \n", str);
fprintf(fo, "%s", replace);
} else {
fprintf(fo, "%s", str);
}
}
fclose(fp);
return(0);
}
input.txt中:
Maria
rain
manel
Bla bla
rain
Output.text完全和input.txt一样,在它为空之前,所以代码工作正常,除了用strcmp
测试的if块。
问题是在\n
缓冲区末尾的str
。 fgets
在它读取的行的末尾添加了\n
,你需要在比较之前摆脱它。
这就是你需要的:
while (fgets(str, 60, fp) != NULL) {
/* remove \n from at the end of the str buffer*/
char *pos;
if ((pos = strchr(str, '\n')) != NULL)
*pos = '\0';
/* print str enclosed in <> so we can see what str actually contains */
printf("Inside the loop, got the string: <%s>\n", str);
if (strcmp(compare, str) == 0) {
printf("Found it! %s\n", str);
fprintf(fo, "%s\n", replace);
}
else {
fprintf(fo, "%s\n", str);
}
}
查看代码中的注释以获得解释。
您的方法失败,因为从输入文件中读取的行包含一个尾随换行符'\n'
,使得比较返回非零。
您可以在与搜索字符串进行比较之前剥离换行符。
请注意,还有其他问题:
argc > 4
来验证是否已经传递了足够的命令行参数。"w+"
中打开输出文件,"w"
更简单,更好。这是一个改进版本:
#include <stdio.h>
#include <string.h>
int main(int argc, char **argv) {
FILE *fp, *fo;
char *compare, *replace;
char line[256];
if (argc <= 4) {
printf("missing command line arguments\n");
return 1;
}
fp = fopen(argv[1], "r");
if (fp == NULL) {
perror("Error opening input file");
return 1;
}
compare = argv[2];
fo = fopen(argv[3], "w");
if (fo == NULL) {
perror("Error opening output file");
return 1;
}
replace = argv[4];
while (fgets(line, sizeof line, fp) != NULL) {
line[strcspn(line, "\n")] = '\0';
if (strcmp(line, compare) == 0) {
printf("fount it!);
fprintf(fo, "%s\n", replace);
} else {
fprintf(fo, "%s\n", line);
}
}
fclose(fp);
fclose(fo);
return 0;
}
请注意,长行将被分成适合line
数组的块,因此上述天真方法可能存在误报。
您可以使用此内循环完全删除此限制:
int c;
int pos = 0;
int cmplen = strlen(compare);
for (;;) {
c = getc(fp);
if (c == '\n' || c == EOF) {
if (pos == cmplen) {
fprintf(fo, "%s", replace);
} else
if (pos > 0) {
fprintf(fo, "%*s", pos, compare);
}
pos = 0;
if (c == EOF)
break;
} else {
if (pos >= 0) {
if (compare[pos] == (char)c) {
pos++;
continue;
}
if (pos > 0) {
fprintf(fo, "%*s", pos, compare);
}
pos = -1;
}
}
putc(c, fo);
}
来自man fgets
char * fgets(char * s,int size,FILE * stream);
fgets()从流中读取最多一个小于大小的字符,并将它们存储到s指向的缓冲区中。读数在EOF或换行符后停止。如果读取换行符,则将其存储到缓冲区中。终止空字节('\ 0')存储在缓冲区中的最后一个字符之后。
所以你需要从缓冲区s
中删除换行符,例如:
c[strlen(c) - 1] = 0 when c[strlen(c) - 1] == '\n'
read.c
#include <stdio.h>
#include <string.h>
/**
* How to compile program:
* gcc read.c -o read
*
* How to run the program:
* .> ./read input.txt rainy output.txt sunny
* (On Windows MinGW compiler, simply:
* .> read input.txt rainy output.txt sunny - without ./)
*
*/
int main (int argc, char **argv) {
FILE *fp, *fo;
char *compare, *replace;
char line[246];
if (argc <= 4){
printf(">Missing arguments on the command line.\n");
printf(">Be sure you run the program as\n\"./read input.txt compare outout.txt replace\"\n\n");
}
/* Opening files for reading */
fp = fopen(argv[1] , "r");
if(fp == NULL){
perror("Error opening input file");
return 1;
}
compare = argv[2];
fo = fopen(argv[3], "w");
if(fo == NULL){
perror("Error opening output file");
return 1;
}
replace = argv[4];
while( fgets (line, (sizeof line), fp)!=NULL ) {
line[strcspn(line, "\n")] = 0;
if(strcmp(compare, line) == 0){
printf("Found it! %s \n", line);
fprintf(fo, "%s\n", replace);
}
else{
fprintf(fo, "%s\n", line);
}
}
fclose(fp);
fclose(fo);
return 0;
}
/*
Important info
strcspn ::
Locate first occurrence of character in string,
after locating the first occurrence of \n, replaces it by 0.
Sources::
https://stackoverflow.com/questions/2693776/removing-trailing-newline-character-from-fgets-input/28462221#28462221
Used to debug:
.>printf("1st: Reads input.txt, removes '\\n' from fgets, and prints it \n");
.>printf("2nd: Compares each line with 'rainy' \n");
.>printf("<%s>\n", line);
*/
input.txt中
cloudy
rainy
chilly
rainy
rainy