我的代码不能正确地用一个单词替换另一个单词
我的代码不能正确地用一个单词替换另一个单词
提问于 2019-01-21 06:38:29
我只是用c写了一个简单的代码，它应该从文件中提取一个文本，并用一个单词替换另一个单词。但是，我不知道为什么，我的代码只是替换了从第二个字母开始的单词。我做错了什么？这是我的代码：
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *f;
char sir[20];
if ((f=fopen("fis.txt","r"))==NULL)
{
printf("Not ok");
exit(1);
}
gets(sir);
fscanf(f, "%s",sir);
printf("Give the word you are looking for and the word to replace it with");
getchar();
char s1[10],s2[10];
gets(s1);
gets(s2);
char *p, aux[100];
while (p=strstr(sir,s1))
{
strcpy(aux,p+strlen(s1));
strcpy(p,s2);
strcpy(p+strlen(s2),aux);
puts(sir);
}
}回答 2
Stack Overflow用户
发布于 2019-01-21 07:50:14
我发现你的方法有点太复杂了，只需移动指针就可以简单得多。以下是一个粗略的(1)草图：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
/* Input file */
FILE *f;
/* Buffer for content of input-file */
char sir[100] = { 0 };
/* Temporary memory to hold the result */
/* char tmp[100] = {0}; */
/* Memory for the word to find and the one to replace */
char s1[10], s2[10];
/* Pointer to the occurrence of the word to replace */
char *p;
/* Pointer to sir, the memory holding the content of the file */
char *c;
if ((f = fopen("fis.txt", "r")) == NULL) {
printf("Not ok");
exit(EXIT_FAILURE);
}
/* Read content of file, leave room for the final `\0` */
/* TODO: check return of fread() */
fread(sir, 99, 1, f);
printf("Give the word you are looking for and the word to replace it with: \n");
/* TODO: check return of scanf() */
/* HINT: you should read the two words separately. Ask for the word to find first,
* read it and repeat that for the word to replace. */
scanf("%9s %9s", s1, s2);
/* Give user a change to stay in control. */
printf("You are looking for %s and want it to be replaced with %s\n", s1, s2);
/* We want to move through the input, we can do it quite comfortably with a pointer */
c = sir;
/* For every occurrence of the word to replace */
while ((p = strstr(c, s1)) != NULL) {
/* Print all characters up to the pointer p */
/* TODO: change it to fill tmp instead. */
/* HINT: I would use a pointer to tmp to do it but check the length! */
while (c < p) {
printf("%c", *c);
c++;
}
/* Print the replacement / fill tmp */
printf("%s", s2);
/* Move the pointer to sir to the point in sir after the original word */
c = p + strlen(s1);
}
/* Print / fill tmp with the rest of sir. Check the length if you use tmp! */
printf("%s", c);
/* Get outta here! */
exit(EXIT_SUCCESS);
}Stack Overflow用户
发布于 2019-01-21 15:59:51
继续我的评论，永远不要使用gets()，它是可怕的不安全的，并且容易被缓冲区溢出所利用。相反，对于面向行输入，请使用fgets或POSIX getline。
在读取文本文件作为输入时，99%的情况下使用面向行的输入函数是正确的。它在这里可以很好地工作，但您必须确保您的行缓冲区足以容纳您预期的最大行。
您也不应该尝试修改您正在“就地”搜索的文件。虽然要查找和替换的单词的长度可能完全相同，但您必须小心，否则会损坏文件。写到一个新的文件，你可以自由地让你的‘查找’和‘替换’的词具有不同的长度。
假设您的单词将完全包含在您读取的行中(并且不使用连字符或以其他方式拆分多行)，您可以简单地读取每一行，将指针分配给行中的起始字符，然后沿行移动指针，当字符与查找字中的字符匹配时保留索引，并在字符不同时输出替换。您必须考虑如何处理重置索引和处理部分匹配，但这只是一个简单的算术运算。
例如，如果您有一个指向打开的文件流(例如fp)的指针，该指针将每行内容读取到buf中，您的单词将在find中查找，而替换字符串将在repl中查找，则可以执行类似以下操作：
lfind = strlen (find); /* length of replacement */
while (fgets (buf, MAXCH,fp)) { /* read each line in file */
p = buf; /* pointer to buf */
while (*p) {
if (*p == find[ndx]) /* if matches char in find */
ndx++; /* advance index */
else { /* otherwise */
if (ndx) { /* if find chars matched */
if (ndx == lfind) /* if full word found */
fputs (repl, stdout); /* output replacement */
else { /* otherwise */
int tmp = repl[ndx]; /* save char at ndx */
repl[ndx] = 0; /* nul-terminate repl */
fputs (repl, stdout); /* output replacement */
repl[ndx] = tmp; /* restore char at ndx */
}
ndx = 0; /* zero index */
}
putchar (*p); /* output current char */
}
p++;
}
}
fclose (fp); /* close file */
if (ndx) { /* if partial match at end of file */
repl[ndx] = 0; /* nul-terminate repl at index */
fputs (repl, stdout); /* output final chars */
}(您应该进一步检查每一行的strlen是否合适并且没有被截断，否则您要查找的单词的不同部分可能会出现在两个不同的缓冲区中--这由您决定)
还要注意在循环退出后的检查，如果ndx为非零，则检查是否输出任何最后的字符。
在一个简短的示例中，以文件名读取和find/repl字符串作为程序的参数1、2、3(如果没有作为参数提供，则将提示find/repl )，您可以执行类似以下操作：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXCH 1024
#define MAXWD 128
void handle_args (int argc, char **argv, char *find, char *repl);
int main (int argc, char **argv) {
size_t lfind, ndx = 0;
char buf[MAXCH], find[MAXWD] = "", repl[MAXWD] = "", *p;
FILE *fp = NULL;
if (argc < 2 ) { /* validate at least one argument given */
fprintf (stderr, "error: insufficient input, usage: "
"%s filename [find, repl]\n", argv[0]);
return 1;
}
if (!(fp = fopen (argv[1], "r"))) { /* validate file open for reading */
perror ("file open failed");
return 1;
}
handle_args (argc, argv, find, repl); /* set/prompt for find/repl */
lfind = strlen (find); /* length of replacement */
while (fgets (buf, MAXCH,fp)) { /* read each line in file */
p = buf; /* pointer to buf */
while (*p) {
if (*p == find[ndx]) /* if matches char in find */
ndx++; /* advance index */
else { /* otherwise */
if (ndx) { /* if find chars matched */
if (ndx == lfind) /* if full word found */
fputs (repl, stdout); /* output replacement */
else { /* otherwise */
int tmp = repl[ndx]; /* save char at ndx */
repl[ndx] = 0; /* nul-terminate repl */
fputs (repl, stdout); /* output replacement */
repl[ndx] = tmp; /* restore char at ndx */
}
ndx = 0; /* zero index */
}
putchar (*p); /* output current char */
}
p++;
}
}
fclose (fp); /* close file */
if (ndx) { /* if partial match at end of file */
repl[ndx] = 0; /* nul-terminate repl at index */
fputs (repl, stdout); /* output final chars */
}
return 0;
}
/* simple function to set find/repl from command line, or
* prompt for input if no arguments given.
*/
void handle_args (int argc, char **argv, char *find, char *repl)
{
if (argc < 3) {
fputs ("enter find word: ", stdout);
if (scanf ("%127s", find) != 1) {
fputs ("error: invalid input.\n", stderr);
exit (EXIT_FAILURE);
}
}
else {
size_t len = strlen (argv[2]);
if (len < MAXWD)
memcpy (find, argv[2], len + 1);
else {
fputs ("error: find argument too long.\n", stderr);
exit (EXIT_FAILURE);
}
}
if (argc < 4) {
fputs ("enter repl word: ", stdout);
if (scanf ("%127s", repl) != 1) {
fputs ("error: invalid input.\n", stderr);
exit (EXIT_FAILURE);
}
}
else {
size_t len = strlen (argv[3]);
if (len < MAXWD)
memcpy (repl, argv[3], len + 1);
else {
fputs ("error: repl argument too long.\n", stderr);
exit (EXIT_FAILURE);
}
}
}输入文件示例
$ cat ../dat/qbfox3.txt
A quick brown fox jumps over the lazy dog.
A slow green dog jumps on top of the blue cat.
A quick blue bird flew over the lazy dog too.示例使用/输出
$ ./bin/file_replace_fgets_stdout ../dat/qbfox3.txt dog duck
A quick brown fox jumps over the lazy duck.
A slow green duck jumps on top of the blue cat.
A quick blue bird flew over the lazy duck too.或检查第一个和最后一个字符替换的边角大小写，例如
$ ./bin/file_replace_fgets_stdout ../dat/qbfox3.txt "." "*"
A quick brown fox jumps over the lazy dog*
A slow green dog jumps on top of the blue cat*
A quick blue bird flew over the lazy dog too*
$ ./bin/file_replace_fgets_stdout ../dat/qbfox3.txt A B
B quick brown fox jumps over the lazy dog.
B slow green dog jumps on top of the blue cat.
B quick blue bird flew over the lazy dog too.仔细检查一下，如果你还有其他问题，请告诉我。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54281647
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