Unix Shell: Process Schedule(2)

1. batch command
batch command just make different commands run simultaneously
terminal:
1) run batch command, then we are allowed to put in the command list will be put into the batch queue
2) Put in two following commands then type Ctrl D
./script_1
echo "Hello world!" > temp2.txt
3) List the temp file generated. Both files are generated.
4 - 5) Print out the file content

 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ batch  
 warning: commands will be executed using /bin/sh  
 at> ./script_1  
 at> echo "Hello world!" >temp2.txt  
 at> <EOT>  
 job 18 at Sun Jul 27 15:24:00 2014  
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ ls -lrt temp*  
 -rw-rw-r-- 1 aubinxia aubinxia 13 Jul 27 15:25 temp.txt  
 -rw-rw-r-- 1 aubinxia aubinxia 13 Jul 27 15:25 temp2.txt  
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ cat temp.txt  
 Hello world!  
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ cat temp2.txt  
 Hello world!  

2. crontab
crontab is used to run specified command at scheduled time, it is very helpful run some "maintaining tsk" which needs to run multiple times at different time period.

crontab file format:
mm     hh       dd       mon    weekeday            command
00-59  00-23  01-31  01-12  0-6(0=Sunday)

hyphen means range, * means every choice

owntab:
1) First line means that system should run ls command every minute
2) Second line means that system should run ls command at every Sunday's 23:15

 0-59 * * * * ls >>/home/aubinxia/Desktop/xxdev/temp.txt  
 15 23 * * 0 ls >>/home/aubinxia/Desktop/xxdev/temp.txt  

terminal:
1) -l option make crontab list current tab schedule
2) If there is no schedule now, we add our own owntab schedule
3) After some minutes, print out the content of temp.txt, we found that crontab is working now, it starts output the content into temp.txt. Based on its content, we can know that crontab is running the command at user's home directory.
4) Use -r option to remove the current tab schedule
5) Use -l option to list current tab schedule, we find that all schedules have been removed.

 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ crontab -l  
 no crontab for aubinxia  
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ crontab owntab  
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ cat temp.txt  
 Desktop  
 Documents  
 Downloads  
 examples.desktop  
 Music  
 Pictures  
 Public  
 script_1  
 script_1~  
 Templates  
 Videos 
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ crontab -r
 aubinxia@aubinxia-fastdev:~/Desktop/xxdev$ crontab -l
 no crontab for aubinxia