在C中使用PCRE搜索和替换文件

我想用C解析shell样式的键值配置文件，并根据需要替换值。一个示例文件可能看起来像

FOO="test"
SOME_KEY="some value here"
ANOTHER_KEY="here.we.go"
SOMETHING="0"
FOO_BAR_BAZ="2"

要查找值，我想使用正则表达式。我是一个初学者与PCRE库，所以我创建了一些代码来测试。这个应用程序有两个参数:第一个是要搜索的键。第二个是要填入双引号的值。

#include <pcre.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#define OVECCOUNT 30
int main(int argc, char **argv){
    const char *error;
    int   erroffset;
    pcre *re;
    int   rc;
    int   i;
    int   ovector[OVECCOUNT];
    char regex[64];
    sprintf(regex,"(?<=^%s=\").+(?<!\")", argv[1]);
    char *str;
    FILE *conf;
    conf = fopen("test.conf", "rw");
    fseek(conf, 0, SEEK_END);
    int confSize = ftell(conf)+1;
    rewind(conf);
    str = malloc(confSize);
    fread(str, 1, confSize, conf);
    fclose(conf);
    str[confSize-1] = 'n';
    re = pcre_compile (
         regex,       /* the pattern */
         PCRE_CASELESS | PCRE_MULTILINE, /* default options */
         &error,               /* for error message */
         &erroffset,           /* for error offset */
         0);                   /* use default character tables */
    if (!re) {
        printf("pcre_compile failed (offset: %d), %sn", erroffset, error);
        return -1;
    }
    rc = pcre_exec (
        re,                   /* the compiled pattern */
        0,                    /* no extra data - pattern was not studied */
        str,                  /* the string to match */
        confSize,          /* the length of the string */
        0,                    /* start at offset 0 in the subject */
        0,                    /* default options */
        ovector,              /* output vector for substring information */
        OVECCOUNT);           /* number of elements in the output vector */
    if (rc < 0) {
        switch (rc) {
            case PCRE_ERROR_NOMATCH:
                printf("String didn't match");
                break;
            default:
                printf("Error while matching: %dn", rc);
                break;
        }
        free(re);
        return -1;
    }
    for (i = 0; i < rc; i++) {
        printf("========nlength of vector: %dnvector[0..1]: %d %dnchars at start/end: %c %cn", ovector[2*i+1] - ovector[2*i], ovector[0], ovector[1], str[ovector[0]], str[ovector[1]]);
        printf("file content length is %dn========n", strlen(str));
    }
    int newContentLen = strlen(argv[2])+1;
    char *newContent = calloc(newContentLen,1);
    memcpy(newContent, argv[2], newContentLen);
    char *before = malloc(ovector[0]);
    memcpy(before, str, ovector[0]);
    int afterLen = confSize-ovector[1];
    char *after = malloc(afterLen);
    memcpy(after, str+ovector[1],afterLen);
    int newFileLen = newContentLen+ovector[0]+afterLen;
    char *newFile = calloc(newFileLen,1);
    sprintf(newFile,"%s%s%s", before,newContent, after);
    printf("%sn", newFile);
    return 0;
}

这段代码在某些情况下是可以工作的，但是如果我想替换FOO或ANOTHER_KEY，就有问题了。

$ ./search_replace.out FOO baz
========
length of vector: 5
vector[0..1]: 5 10
chars at start/end: b "
file content length is 94
========
FOO="9@baz"
SOME_KEY="some value here"
ANOTHER_KEY="here.we.go"
SOMETHING="0"
FOO_BAR_BAZ="2"
$ ./search_replace.out ANOTHER_KEY insert
========
length of vector: 10
vector[0..1]: 52 62
chars at start/end: h "
file content length is 94
========
FOO="baaar"
SOME_KEY="some value here"
ANOTHER_KEY=")insert"
SOMETHING="0"
FOO_BAR_BAZ="2"

现在如果我稍微改变一下输入文件的格式为

TEST="new inserted"
FOO="test"
SOME_KEY="some value here"
ANOTHER_KEY="here.we.go"
SOMETHING="0"
FOO_BAR_BAZ="2"

代码工作正常。我不明白为什么代码在这里的行为不同