C++ source.
"Croncpp" is a light library (iot-friendly) for processing CRON expressions.
It implements two basic operations: find the next date or find the last date of execution of a periodic processing defined in cron format.
This allows to find the current status of the iot device after rebooting and plan its next state ...
| cron() | initialze a cron object |
| cron( std::string( `a cron format definition (see below)` ) | initialize and set a cron job object |
| std::string cron.expression() | return the command of the job |
| cron& cron.assign( std::string ) | assign a new cron definition |
| cron = std:string() | assign a new cron definition |
| cron& cron.clear() | clear the cron object |
| bool cron.error() (return true on error) | allows to verify the cron expression |
| const time_t cron.nextDate( std::tn* ) | Find the next rawtime of the cron job (-1 on error) |
| const time_t cron.nextDate( const time_t* ) | Find the next rawtime of the cron job |
| const time_t cron.nextDate( const time_t& ) | Find the next rawtime of the cron job |
| const time_t cron.previousDate( std::tn ) | give the last rawtime of the previous cron job exec |
| const time_t cron.previousDate( const time_t* ) | give the last rawtime of the previous cron job exec |
| const time_t cron.previousDate( const time_t& ) | give the last rawtime of the previous cron job exec |
Format of a cron string : "S M H d m w [Y] cmd" - (Year is optional ; default limit values of the year: +/- 8 years relative to the current year).
# define out /*
g++ -o main $0 cron.cpp; exit $?
# define out */
# undef out
#include <string>
#include <iostream>
#include "cron.h"
int main() {
time_t rawtime(time(NULL)), result;
char buffer [80];
std::string cronexpr( "*/10 55 * * apr * 2021-2025 myCommand" );
// Or:
// localtime( &rawtime );
// cron myCron = "*/10 55 * * apr * 2021-2025 myCommand";
// rawtime = myCron.nextDate( &rawtime );
// std::cout << localtime( &rawtime ) << std::endl;
// ...
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&rawtime) );
std::cout << "Now() is " << rawtime << " (" << buffer << ")" << std::endl << "Cron expression is: " << cronexpr << std::endl;
// Next date:
result = cron( cronexpr ).nextDate( rawtime );
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&result) );
std::cout << "The next \"" << cron( cronexpr ).expression() << "\" task will be performed at: " << result << " (" << buffer << ")." << std::endl;
// Previous date:
result = cron( cronexpr ).previousDate( rawtime );
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&result) );
std::cout << "The last execution of the \"" << cron( cronexpr ).expression() << "\" task was at: " << result << " (" << buffer << ")." << std::endl;
return 0;
}
Now() is 1656593363 (2022/06/30 02:49:23)
Cron expression is: */10 55 * * apr * 2021,2025 myCommand
The next "myCommand" task will be performed at: 1743504900 (2025/04/01 00:55:00).
The last execution of the "myCommand" task was at: 1617274500 (2021/04/30 23:55:50)
# define out /*
g++ -o main $0 cron.cpp && ./main; exit $?
# define out */
# undef out
#include <string>
#include <vector>
#include <iostream>
#include "cron.h"
int main() {
std::vector<std::string> crontab = {
"5-55 55 * * apr * myCmd1",
"* 25-30 * * * * myCmd2",
"*/10 55 * * apr * 2021,2025 myCmd3",
"* 05-30 * * * 2-3 * myCmd4",
"* * * 31 * * myCmd5"
};
char buffer [80];
time_t t, Now(time(NULL));
time_t rawtime( cron( crontab[0] ).nextDate( Now ) );
std::string job;
cron c;
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&Now) );
std::cout << "Now() is " << Now << " (" << buffer << "):" << std::endl << std::endl;
for( auto& x : crontab ){
c.assign(x);
t = c.nextDate( Now );
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime( &t ) );
std::cout << "The job \"" << c.expression() << "\" will be lanched at: " << t << " (" << buffer << ") - \"" << x << "\"" << std::endl;
if ( t != -1 && t < rawtime ){
rawtime = t; job = c.expression();
} }
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&rawtime) );
std::cout << std::endl << "The next job will be \"" << job << "\" at: " << rawtime << " (" << buffer << ")." << std::endl;
rawtime=-1; for( auto& x : crontab ){
c.assign(x);
t = c.previousDate( Now );
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime( &t ) );
std::cout << "The job \"" << c.expression() << "\" has been lanched at: " << t << " (" << buffer << ") - \"" << x << "\"" << std::endl;
if ( t != -1 && t > rawtime ){
rawtime = t; job = c.expression();
} }
strftime ( buffer, 80, "%Y/%m/%d %H:%M:%S", localtime(&rawtime) );
std::cout << std::endl << "The last job was \"" << job << "\" at: " << rawtime << " (" << buffer << ")." << std::endl << std::endl;
return 0;
}
Now() is 1657317135 (2022/07/08 11:52:15):
The job "myCmd1" will be lanched at: 1680346505 (2023/04/01 00:55:05) - "5-55 55 * * apr * myCmd1"
The job "myCmd2" will be lanched at: 1657319100 (2022/07/08 12:25:00) - "* 25-30 * * * * myCmd2"
The job "myCmd3" will be lanched at: 1743504900 (2025/04/01 00:55:00) - "*/10 55 * * apr * 2021,2025 myCmd3"
The job "myCmd4" will be lanched at: 1657620300 (2022/07/12 00:05:00) - "* 05-30 * * * 2-3 * myCmd4"
The job "myCmd5" will be lanched at: 1659261600 (2022/07/31 00:00:00) - "* * * 31 * * myCmd5"
The next job will be "myCmd2" at: 1657319100 (2022/07/08 12:25:00).
The job "myCmd1" has been lanched at: 1651398955 (2022/04/30 23:55:55) - "5-55 55 * * apr * myCmd1"
The job "myCmd2" has been lanched at: 1657315800 (2022/07/08 11:30:00) - "* 25-30 * * * * myCmd2"
The job "myCmd3" has been lanched at: 1619862950 (2021/04/30 23:55:50) - "*/10 55 * * apr * 2021,2025 myCmd3"
The job "myCmd4" has been lanched at: 1657186200 (2022/07/06 23:30:00) - "* 05-30 * * * 2-3 * myCmd4"
The job "myCmd5" has been lanched at: 1653991200 (2022/05/31 00:00:00) - "* * * 31 * * myCmd5"
The last job was "myCmd2" at: 1657315800 (2022/07/08 11:30:00).