[英]fscanf() match string in C
I have a file laid out like this: 我有一个这样的文件:
X1034Example
X1234Example2
Y2934Example3
and say I have opened that file and loaded it into *fp
, I now want to match lines like this: "X" followed by 4 digits followed by any string so I assumed that would be something like this: 并说我已打开该文件并将其加载到
*fp
,我现在想要匹配这样的行:“X”后面跟着4个数字后跟任何字符串,所以我假设它会是这样的:
FILE **fp;
if ((*fp = fopen(fileName, "r")) == NULL) {
printf("Unable to read file: %d: %s\n", errno, strerror(errno));
exit(1);
}
int id; char label[64];
fscanf(*fp, "X%4d%s", &id, label)
However, this doesn't work properly and for the file specified I tested using this snippet: 但是,这不能正常工作,对于我使用此代码段测试的文件:
fscanf(*fp, "X%4d%s", &id, label);
printf("%d\n", id);
printf("%s\n", label);
fscanf(*fp, "X%4d%s", &id, label);
printf("%d\n", id);
printf("%s\n", label);
and the output I had was 我的输出是
1
Example
1
Example
is this just due to the non-deterministic behaviour with pointer or am I doing something wrong? 这只是由于指针的非确定性行为或我做错了什么?
Edit 1 编辑1
So adding a space before the X fixed the first issue but now I just realised that some of the labels have spaces in. 所以在X修复第一个问题之前添加一个空格,但现在我才意识到一些标签中有空格。
For example: 例如:
X1245Example Text Here
fscanf(*fp, " X%4d%s", &id, label);
printf("%d\n", id);
printf("%s\n", label);
should produce: 应该产生:
1245
Example Text Here
is this just due to the non-deterministic behaviour with pointer or am I doing something wrong?
这只是由于指针的非确定性行为或我做错了什么?
fscanf(*fp, "X%4d%s", &id, label)
does not consume the leftover '\\n'
of the previous line. fscanf(*fp, "X%4d%s", &id, label)
不消耗前一行的剩余'\\n'
。 See hint: @Some programmer dude . 见提示: @Some程序员老兄 。 The 2nd
fscanf()
simple failed and did not update id, label
. 第二个
fscanf()
简单失败,没有更新id, label
。 Had code checked the fscanf()
return value, this could have been caught earlier. 如果代码检查了
fscanf()
返回值,则可能之前已经捕获过。
Use fscanf(*fp, " X%4d%s", &id, label)
(Add space) or better yet, code fgets()
and then sscanf()
the line and check the return value of the scan. 使用
fscanf(*fp, " X%4d%s", &id, label)
(添加空格)或更好,编码fgets()
然后sscanf()
行并检查扫描的返回值。
int id; char label[64];
char buffer[sizeof label * 2]; // form a generous buffer
if (fgets(buffer, sizeof buffer, stdin)) {
if (sscanf(*fp, "X%4d%63s", &id, label) == 2) {
printf("%d\n", id);
printf("%s\n", label);
} else {
Failed();
}
}
To read the rest of the line , instead of "%s"
, : 要阅读该行的其余部分 ,而不是
"%s"
,:
if (fgets(buffer, sizeof buffer, stdin)) {
if (sscanf(*fp, "X%4d%63[^\n]", &id, label) == 2) {
printf("%d\n", id);
printf("<%s>\n", label); // added <> to help denote spaces
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