pwent.c

建立一个模拟数据库来存储你的登录用户名、密码

/*
    A simple library for password databases.  Tobias Gedell 2007
*/

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include "pwent.h"


#define LINE_BUFFER_LENGTH  1000


/*
    Return pointer to password entry for specified user.
    
    Upon error, or if the user couldn't be found, NULL is returned.
    
    Note: The returned pointer points to static data.
*/
mypwent *mygetpwnam(char *name)
{
    FILE *file;
    char buffer[LINE_BUFFER_LENGTH];

    static char pwname[LINE_BUFFER_LENGTH], 
                passwd[LINE_BUFFER_LENGTH],
                passwd_salt[LINE_BUFFER_LENGTH];
    static mypwent ent = {pwname, 0, passwd, passwd_salt, 0, 0};
    

    /* Open file, return NULL if it failed. */
    if((file = fopen(MYPWENT_FILENAME, "rb")) == NULL) return NULL;
    
    /* Read each line, looking for the right entry. */
    while(fgets(buffer, sizeof(buffer), file) != NULL)
    {
        if(sscanf(buffer, "%[^:]:%d:%[^:]:%[^:]:%d:%d",
            ent.pwname, &ent.uid, ent.passwd,
            ent.passwd_salt, &ent.pwfailed, &ent.pwage) != 6)
                break;
        
        if(strcmp(pwname, name) == 0)
        {
            fclose(file);
            return &ent;
        }
    }
    
    fclose(file);

    return NULL;
}

/*
    Update password entry for user.
    
    Upon error, or if the user couldn't be found, -1 is returned,
    otherwise 0.
*/
int mysetpwent(char *name, mypwent *pw)
{
    FILE *file;
    FILE *newfile;
    char buffer[LINE_BUFFER_LENGTH];
    char pwname[LINE_BUFFER_LENGTH];
    
    int status = -1;


    if((file = fopen(MYPWENT_FILENAME, "rb")) == NULL) return -1;
    if((newfile = fopen(MYPWENT_TMP_FILENAME, "wb")) == NULL)
        { fclose(file); return -1; }
    
    /* Read each line, looking for the right entry. */
    while(fgets(buffer, sizeof(buffer), file) != NULL)
    {
        if(sscanf(buffer, "%[^:]", pwname) != 1) { status = -1; break; }

        /* See if we found the entry to be updated. */
        if(strcmp(pwname, name) == 0)
        {
            if(snprintf(buffer, sizeof(buffer), "%s:%d:%s:%s:%d:%d\n",
                pw->pwname, pw->uid, pw->passwd,
                pw->passwd_salt, pw->pwfailed, pw->pwage) >= sizeof(buffer))
                { status = -1; break; }
                
            status = 0;
        }
        
        if(fputs(buffer, newfile) < 0) { status = -1; break; }
    }

    fclose(newfile);
    fclose(file);
    
    /* Swap files if user successfully updated. */
    if(status == 0)
    {
        if(rename(MYPWENT_TMP_FILENAME, MYPWENT_FILENAME) != 0) status = -1;
    }
    else unlink(MYPWENT_TMP_FILENAME);
    
    return status;
}