Linux cron 源码剖析

背景及 busybox 介绍流程图数据结构typedef struct CronFile { struct CronFile *cf_next; struct CronLine *cf_lines; char cf_username; smallint cf_wants_starting; / bool: one or more jobs ready / smallint cf_has_running; / bool: one or more jobs running / smallint cf_deleted; / marked for deletion (but still has running jobs) */} CronFile;typedef struct CronLine { struct CronLine *cl_next; char cl_cmd; / shell command / pid_t cl_pid; / >0:running, <0:needs to be started in this minute, 0:dormant /#define START_ME_REBOOT -2#define START_ME_NORMAL -1#if ENABLE_FEATURE_CROND_CALL_SENDMAIL int cl_empty_mail_size; / size of mail header only, 0 if no mailfile */ char cl_mailto; / whom to mail results, may be NULL */#endif char cl_shell; / ordered by size, not in natural order. makes code smaller: / char cl_Dow[7]; / 0-6, beginning sunday / char cl_Mons[12]; / 0-11 / char cl_Hrs[24]; / 0-23 / char cl_Days[32]; / 1-31 / char cl_Mins[60]; / 0-59 */} CronLine;cron 使用方法分析代码