c - C 中的 fork 线程正在互相写入标准输出

Question

我写了一个小守护进程。

这是守护进程的流程，一般来说:

1. 获取变量

2. 从数据库(可能是 MySQL 或 Oracle)中获取满足查询参数的所有行(在本例中获取具有当前时间的所有行)。

3. 如果找到任何行，则为每一行运行一个 Perl 脚本(使用 execv)。

这个守护进程运行良好，但问题是当我有两行或更多行从查询返回时，它们开始，但 Perl 脚本输出是混合的。它们应该独立运行而不会相互干扰。

我做错了什么吗？

这是内存泄漏吗？

这是我的代码:

/*
 ============================================================================
 Name        : main.c
 Description : Daemon for scheduler
 ============================================================================
 */

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <syslog.h>
#include <string.h>
#include <strings.h>
#include <regex.h>
#include <time.h>

#ifdef MYSQL_CODE
#include <mysql.h>
#endif

#ifdef ORACLE_CODE
#include <ocilib.h>
#endif

#define DAEMON_NAME "schedulerd"

void start_job(char *automation_user,char *automation_path,char *automation_log_path, char *id, char *site, char *db_type,char *db_host,char *db_user,char *db_password,char *db_schemata){

    pid_t pid;
    pid = fork();

    if (pid < 0) { exit(EXIT_FAILURE); }

    //We got a good pid, Continue to the next result
    if (pid > 0) {
        return;
    }

    char *file_format = "scheduler";
    char *seperator = "_";
    char *postfix = "_XXXXXX";
    char *extension = ".log";

    //get Time
    time_t now;
    struct tm *now_tm;
    char hour[2],min[2],sec[2];

    now = time(NULL);
    now_tm = localtime(&now);
    sprintf(hour, "%d", now_tm->tm_hour);
    sprintf(min, "%d", now_tm->tm_min);
    sprintf(sec, "%d", now_tm->tm_sec);

    char *str  = (char *)automation_log_path;
    strcat(str,(char *)file_format);
    strcat(str,seperator);
    strcat(str,hour);
    strcat(str,seperator);
    strcat(str,min);
    strcat(str,seperator);
    strcat(str,sec);
    strcat(str,postfix);

    // buffer to hold the temporary file name
    char nameBuff[128];

    int filedes = -1;

    // memset the buffers to 0
    memset(nameBuff,0,sizeof(nameBuff));

    // Copy the relevant information in the buffers
    strncpy(nameBuff,str,128);

    // Create the temporary file, this function will replace the 'X's
    filedes = mkstemp(nameBuff);

    if(filedes<1)
    {
        syslog (LOG_NOTICE, "Creation of temp file [%s] failed with error [%s]\n",nameBuff,strerror(errno));
    }else{
        mode_t perm = 0644;
        fchmod(filedes, perm); //Change permission to the file so everyone can read

        close(filedes); // Close created file
        //Rename file
        int ret;
        char newname[128];
        sprintf(newname, "%s%s", nameBuff,extension);
        ret = rename(nameBuff, newname);
        if(ret != 0) {
            syslog (LOG_NOTICE, "Renaming  of temp file %s to %s failed \n",nameBuff,newname);
            exit(EXIT_FAILURE);
        }

        char statement[256];
        sprintf(statement, "UPDATE scheduler_list SET log_file='%s' WHERE id='%s'", newname,id);
        syslog (LOG_NOTICE,"Adding to DB : %s\n", statement);

        char command[2048];
        sprintf(command, "cd %s ; ./runner.pl -site %s -log %s -scheduler_id %s -command \\\"./run_me.pl\\\"", automation_path,site,newname,id);
        //sprintf(command, "cd /net/10.7.5.50/opt/trunk/ ; ./runner.pl -site %s -log %s -scheduler_id %s -command \\\"./run_me.pl\\\"",site,newname,id);

        if (strcasestr(db_type,"mysql")){/* mysql */
#ifdef MYSQL_CODE
            MYSQL *conn;
            //mysql_free_result(res); // Free mysql
            conn = mysql_init(NULL);
            /* Connect to database */
            if (!mysql_real_connect(conn, db_host,db_user, db_password, db_schemata, 0, NULL, 0)) {
                syslog (LOG_NOTICE,"%s\n", mysql_error(conn));
                exit(EXIT_FAILURE);
            }

            if (mysql_query(conn,statement)) {
                syslog (LOG_NOTICE,"%s\n", mysql_error(conn));
                exit(EXIT_FAILURE);
            }
#endif
        }else{
#ifdef ORACLE_CODE
            OCI_Connection* cn;
            OCI_Statement* st;
            OCI_Initialize(NULL, NULL, OCI_ENV_DEFAULT);
            char query_command[128];
            sprintf(query_command, "%s:1521/%s", db_host,db_schemata);
            cn = OCI_ConnectionCreate(query_command, db_user, db_password, OCI_SESSION_DEFAULT);
            st = OCI_StatementCreate(cn);
            OCI_Prepare(st, statement);
            OCI_Execute(st);
            OCI_Commit(cn);
            OCI_Cleanup();
#endif
        }

        char *args[] = {"sudo", "-u", automation_user, "bash","-c",command,NULL};

        FILE *log_file_h = fopen(newname, "w");
        if (log_file_h == NULL)
        {
            syslog (LOG_NOTICE,"Error opening file %s !\n",newname);
            exit(EXIT_FAILURE);
        }

        syslog (LOG_NOTICE,"Starting scheduler job %s , command : %s",id, command);
        fclose(log_file_h);

        execv("/usr/bin/sudo",args);
        syslog (LOG_NOTICE,"Failed to start job %s ",id);
        perror("error");
    }
    exit(EXIT_FAILURE);
}

void process(char *automation_user,char *automation_path, char *automation_log_path ,char *db_type,char *db_host,char *db_user,char *db_password,char *db_schemata){

    if (strcasestr(db_type,"mysql")){/* mysql */
#ifdef MYSQL_CODE
        MYSQL *conn;
        MYSQL_RES *res;
        MYSQL_ROW row;
        conn = mysql_init(NULL);
        /* Connect to database */
        if (!mysql_real_connect(conn, db_host,db_user, db_password, db_schemata, 0, NULL, 0)) {
            syslog (LOG_NOTICE,"%s\n", mysql_error(conn));
            return;
        }
        /* send SQL query */
        if (mysql_query(conn, "SELECT id,site from scheduler_list where start_date = DATE_FORMAT(now(),'%Y-%m-%d %k:%i:00') AND id != father_id AND run='yes'")) {
            syslog (LOG_NOTICE,"%s\n", mysql_error(conn));
            return;
        }
        res = mysql_use_result(conn);
        /* output table name */
        while ((row = mysql_fetch_row(res)) != NULL){
            char *id = malloc(strlen(row[0]) +1);
            strcpy(id,row[0]);
            char *site = malloc(strlen(row[1]) +1);
            strcpy(site,row[1]);

            start_job(automation_user,automation_path,automation_log_path,id,site,db_type, db_host,db_user,db_password,db_schemata);
        }
        /* close connection */
        mysql_free_result(res);
        mysql_close(conn);
#endif
    }else{/* oracle */
#ifdef ORACLE_CODE
        OCI_Connection* cn;
        OCI_Statement* st;
        OCI_Resultset* rs;
        OCI_Initialize(NULL, NULL, OCI_ENV_DEFAULT);
        char query_command[128];
        sprintf(query_command, "%s:1521/%s", db_host,db_schemata);
        cn = OCI_ConnectionCreate(query_command, db_user, db_password, OCI_SESSION_DEFAULT);
        st = OCI_StatementCreate(cn);

        OCI_ExecuteStmt(st, "SELECT id,site from scheduler_list where to_char(start_date, 'yyyy-mm-dd hh24:mi')  =  to_char(SYSDATE, 'yyyy-mm-dd hh24:mi')  AND id != father_id AND run='yes'");

        rs = OCI_GetResultset(st);
        while (OCI_FetchNext(rs)){

            char *id = malloc(strlen(OCI_GetString(rs, 1)) +1);
            strcpy(id,OCI_GetString(rs,1));
            char *site = malloc(strlen(OCI_GetString(rs,2)) +1);
            strcpy(site,OCI_GetString(rs,2));
            start_job(automation_user,automation_path,automation_log_path,id,site,db_type, db_host,db_user,db_password,db_schemata);
        }
        OCI_Cleanup();
#endif
    }


}

char * set_conf_param (char *line, int addSlash){
    char *param =  malloc(strlen(line) + 2 + addSlash);
    strcpy(param,line);
    param = strchr(line,'=');
    param = param+1; //Remove '='
    strtok(param, "\n"); //remove /n
    if (addSlash == 1){
        int len = strlen(param);
        param[len] = '/';
        param[len+1] = '\0';
    }
    return strdup(param);
}

int main(int argc, char *argv[]) {
        FILE * fp;
        char * line = NULL;
        size_t len = 0;
        int found_db = 0;
        ssize_t read;
        pid_t pid, sid;
        char *automation_user=NULL,*automation_log_path=NULL ,*db_type=NULL, *db_host=NULL , *db_user=NULL, *db_password=NULL, *db_schemata=NULL;
        char *automation_path = getenv("AUTOMATION_PATH");
        //char *automation_path = "/net/10.7.5.50/opt/trunk/";

        char *automation_user_search = "automation_user=";
        char *automation_log_path_search = "automation_log=";
        char *db_type_search = "type=";
        char *db_host_search = "host=";
        char *db_user_search = "user=";
        char *db_password_search = "password=";
        char *db_schemata_search = "schemata=";
        const char comment = '#';
        /* Change the working directory to the root directory */
        /* or another appropriated directory */
        chdir(automation_path);

        //Set our Logging Mask and open the Log
        setlogmask(LOG_UPTO(LOG_NOTICE));
        openlog(DAEMON_NAME, LOG_CONS | LOG_NDELAY | LOG_PERROR | LOG_PID, LOG_USER);

        syslog(LOG_NOTICE, "Entering Daemon");

        //Read framework.conf
        fp = fopen("framework.conf", "r");
        if (fp == NULL){
            syslog (LOG_NOTICE,"Failed to open framework.conf");
            exit(1);
        }

        //Read framework.conf
        fp = fopen("framework.conf", "r");
        if (fp == NULL){
            syslog (LOG_NOTICE,"Failed to open framework.conf");
            exit(1);
        }
        while ((read = getline(&line, &len, fp)) != -1) {

            //If line commented
            if (strchr(line,comment) != NULL){
                continue;
            }

            if (strstr(line,automation_user_search) != NULL){
                automation_user = set_conf_param(line,0);
            }
            else if (strstr(line,automation_log_path_search) != NULL){
                automation_log_path = set_conf_param(line,1);
            }

            else if (db_type!=NULL && strcasestr(line,db_type) != NULL){
                found_db = 1;
            }
            else if (strstr(line,db_type_search) != NULL){
                db_type = set_conf_param(line,0);
            }
            else if (found_db && db_host==NULL && strstr(line,db_host_search) != NULL){
                db_host = set_conf_param(line,0);
            }
            else if (found_db && db_user==NULL && strstr(line,db_user_search) != NULL){
                db_user = set_conf_param(line,0);
            }
            else if (found_db && db_password==NULL && strstr(line,db_password_search) != NULL){
                db_password = set_conf_param(line,0);
            }
            else if (found_db && db_schemata==NULL && strstr(line,db_schemata_search) != NULL){
                db_schemata = set_conf_param(line,0);
            }
        }

        fclose(fp);
        if (line)
            free(line);

        if (automation_user==NULL){
            automation_user = "root";
        }

        //Fork the Parent Process
        pid = fork();

        if (pid < 0) { exit(EXIT_FAILURE); }

        //We got a good pid, Close the Parent Process
        if (pid > 0) { exit(EXIT_SUCCESS); }

        //Change File Mask
        umask(0);

        //Create a new Signature Id for our child
        sid = setsid();
        if (sid < 0) { exit(EXIT_FAILURE); }

        //Close Standard File Descriptors
        close(STDIN_FILENO);
        close(STDOUT_FILENO);
        close(STDERR_FILENO);

        //----------------
        //Main Process
        //----------------
        while(1){
            process(automation_user,automation_path,automation_log_path,db_type,db_host,db_user,db_password,db_schemata);    //Run our Process
            sleep(60);    //Sleep for 60 seconds
        }

        //Close the log
        closelog ();

        exit(EXIT_FAILURE);
}

Answer 1

1. 您似乎没有任何努力写一个 minimal, complete verifiable example .

   这只是您整个程序的转储，包括对您未提供的配置文件的依赖项，以及您未显示其模式的数据库。这些甚至都与您的问题无关。

   至少您编辑了公司名称，但作为引用，它在编辑历史记录中仍然可见。

2. threads in C are writing each other stdout

   我在你的程序中看不到任何线程，而且你也不 fork 线程——你拥有的是子进程

3. ... are writing each other stdout

   好吧，stdout 是从父级继承的，所以所有的子级(和他们的 sudo/bash/perl/任何子级)都写到同一个地方。写入本身被锁定，但可以交错。

   如果您希望它们的输出不交错，让它们写到不同的地方，然后再弄清楚如何显示/组合它们。

   每个子进程的临时文件是一个流行的选择，但请注意，父进程必须跟踪子进程的完成情况，以便知道何时打印然后删除每个文件。此外，您可能应该从终端分 ionic 进程，关闭 stdin，并考虑如何处理 stderr。

4. Is this a memory leak?

   没有。