Zabbix Documentation 3.4

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manual:appendix:command_execution

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manual:appendix:command_execution [2014/09/30 12:54]
127.0.0.1 external edit
manual:appendix:command_execution [2017/10/10 14:42] (current)
martins-v more links to additional info about various command options
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-===== 8 Command execution ​=====+==== 10 Command execution ====
  
-Zabbix uses common functionality ​to execute ​user parameters, remote commands, system.run[] items without "​nowait"​ flagscripts (alert, ​external and global) and some internal ​commands. The command/​script is executed similarly on both UNIX and Windows platforms:+Zabbix uses common functionality ​for external checks, ​user parameters, system.run items, ​custom ​alert scriptsremote ​commands ​and user scripts. 
 + 
 +=== Execution steps === 
 + 
 +The command/​script is executed similarly on both Unix and Windows platforms:
   - Zabbix (the parent process) creates a pipe for communication   - Zabbix (the parent process) creates a pipe for communication
   - Zabbix sets the pipe as the output for the to-be-created child process   - Zabbix sets the pipe as the output for the to-be-created child process
   - Zabbix creates the child process (runs the command/​script)   - Zabbix creates the child process (runs the command/​script)
-  - A new process group (in UNIX) or a job (in Windows) is created for the child process +  - A new process group (in Unix) or a job (in Windows) is created for the child process 
-  - Zabbix reads from the pipe till timeout occurs or no one is writing to the other end (ALL handles/​file descriptors have been closed). Note that the child process can create more processes and exit before they exit or close the handle/file descriptor. +  - Zabbix reads from the pipe until timeout occurs or no one is writing to the other end (ALL handles/​file descriptors have been closed). Note that the child process can create more processes and exit before they exit or close the handle/file descriptor. 
-  - If the timeout has not been reached, Zabbix waits till the initial child process exits or timeout occurs+  - If the timeout has not been reached, Zabbix waits until the initial child process exits or timeout occurs 
 +  - If the initial child process exited and the timeout has not been reached, Zabbix checks exit code of the initial child process and compares it to 0 (non-zero value is considered as execution failure, only for custom alert scripts, remote commands and user scripts executed on Zabbix server and Zabbix proxy)
   - At this point it is assumed that everything is done and the whole process tree (i.e. the process group or the job) is terminated   - At this point it is assumed that everything is done and the whole process tree (i.e. the process group or the job) is terminated
-<note important>​Please note that Zabbix assumes that a command/​script has done processing when the initial child process has exited AND no other process is still keeping the output handle/file descriptor open. When processing is done, ALL created processes are terminated.</​note>​ + 
-<note tip>Read more about [[manual:config:items:​userparameters|user parameters]][[manual:​config:​notifications:​action:​operation:remote_command|remote ​commands]][[manual:​config:​notifications:​media:​script|alert scripts]].</​note>​ +<note important>​Zabbix assumes that a command/​script has done processing when the initial child process has exited AND no other process is still keeping the output handle/file descriptor open. When processing is done, ALL created processes are terminated.</​note>​ 
-<note tip>All double quotes and backslashes in the command are escaped with backslashes and the command is enclosed in double quotes.</​note>​+ 
 +All double quotes and backslashes in the command are escaped with backslashes and the command is enclosed in double quotes. 
 + 
 +=== Exit code checking === 
 + 
 +Exit code are checked with the following conditions:​ 
 + 
 +  *Only for custom alert scripts, remote commands and user scripts executed on Zabbix server and Zabbix proxy. 
 +  *Any exit code that is different from 0 is considered as execution failure. 
 +  *Contents of standard error and standard output for failed executions are collected and available in frontend (where execution result is displayed). 
 +  *Additional log entry is created for remote commands on Zabbix server to save script execution output and can be enabled using LogRemoteCommands agent [[:​manual/​appendix/​config/​zabbix_agentd|parameter]]. 
 + 
 +Possible frontend messages and log entries for failed commands/​scripts:​ 
 +  * Contents of standard error and standard output for failed executions (if any). 
 +  * %%"​%%Process exited with code: N.%%"​%% (for empty output, and exit code not equal to 0). 
 +  * %%"​%%Process killed by signal: N.%%"​%% (for process terminated by a signal, on Linux only). 
 +  * %%"​%%Process terminated unexpectedly.%%"​%% (for process terminated for unknown reasons). 
 + 
 +---- 
 + 
 +Read more about
 + 
 +  * [[:manual/config/items/​itemtypes/​external#​external_check_result|External checks]] 
 +  * [[:manual/​config/​items/​userparameters|User parameters]] 
 +  * [[:manual/config/​items/​itemtypes/​zabbix_agent|system.run]] items 
 +  * [[:manual/​config/​notifications/​media/​script|Custom alert scripts]] 
 +  * [[:manual/​config/​notifications/​action:​operation/remote_command|Remote ​commands]] 
 +  * [[:manual/​web_interface/​frontend_sections/​administration/​scripts|Global ​scripts]]