Flags
You can have special flags on commands that can make the commands only execute when certain things happen. For example, if you want to delay the command by 5 seconds, you can use the d=5; flag.
Start command flags
There is currently only one flag that is compatible with the start commands: the delay flag.
Delay flag
To use the delay flag, simply add d=<number>; to the beginning of the command, replacing the <number> with the number of seconds to delay the command. For example this: d=5;say hello! will execute the command say hello! 5 seconds after the server finishes loading.
Join command flags
Join commands can have several flags: delay, permission, first join, and execute as player.
Delay flag
To use the delay flag, simply add d=<number>; to the beginning of the command, replacing the <number> with the number of seconds to delay the command. For example this: d=5;say hello! will execute the command say hello! 5 seconds after the player joins.
Permission flag
The permission flag will only execute the command if the player has a certain permission. To use it, just add perm=<permission>; to the beginning of the command, replacing <permission> with the permission node you want to check for. For example, this: perm=join.creative;gamemode creative {PLAYER} will put the player in creative mode when they join if they have the permission join.creative.
First join flag
The first join flag will only execute a command if this is the player's first time joining. To use it, simply add [fj] to the beginning of the command.
Execute as player flag
The execute as player flag will make the command execute as the player instead of the console. To use this flag, simple add [p] to the beginning of the command.
Using multiple flags
If you want to use multiple flags in the player join commands, they must be in a certain order: delay, permission, first join, then execute as player. For example, if you had all the flags on a command it would look like this: d=5;perm=join.hi;[fj][p]say hi!.