udev rules with a math expression
I have a udev rule that creates a symlink for serial devices (USB serial ports) using an expression like this: SYMLINK+="MyDevice_%n". The %n assigns the system device node number starting with 0. Is there a way to modify the numbering - instead of %n, perhaps %n+1? Math expressions don't work in a udev rule. I might be able to use a bash script to do the equivalent of echo $((%n+1)) but I'm not sure how to do this in a udev rule. Any helpful suggestions?
serial-port udev
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
add a comment |
I have a udev rule that creates a symlink for serial devices (USB serial ports) using an expression like this: SYMLINK+="MyDevice_%n". The %n assigns the system device node number starting with 0. Is there a way to modify the numbering - instead of %n, perhaps %n+1? Math expressions don't work in a udev rule. I might be able to use a bash script to do the equivalent of echo $((%n+1)) but I'm not sure how to do this in a udev rule. Any helpful suggestions?
serial-port udev
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
add a comment |
I have a udev rule that creates a symlink for serial devices (USB serial ports) using an expression like this: SYMLINK+="MyDevice_%n". The %n assigns the system device node number starting with 0. Is there a way to modify the numbering - instead of %n, perhaps %n+1? Math expressions don't work in a udev rule. I might be able to use a bash script to do the equivalent of echo $((%n+1)) but I'm not sure how to do this in a udev rule. Any helpful suggestions?
serial-port udev
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
I have a udev rule that creates a symlink for serial devices (USB serial ports) using an expression like this: SYMLINK+="MyDevice_%n". The %n assigns the system device node number starting with 0. Is there a way to modify the numbering - instead of %n, perhaps %n+1? Math expressions don't work in a udev rule. I might be able to use a bash script to do the equivalent of echo $((%n+1)) but I'm not sure how to do this in a udev rule. Any helpful suggestions?
serial-port udev
serial-port udev
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
edited Jan 5 '14 at 20:30
JimFred
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
asked Jul 9 '13 at 3:43
JimFredJimFred
1,03177
1,03177
add a comment |
add a comment |
2 Answers
2
active
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votes
Use the udev rules PROGRAM field to execute a /bin/sh echo expression and capture the result using %c, like this...
PROGRAM="/bin/sh -c 'echo $((%n+1))'", SYMLINK+="MyDevice_%c"
The resulting symlink will have the equivalent of MyDevice_$((%n+1)) or MyDevice_1 if %n is zero. The $(()) construct is called "arithmetic expansion" and causes the contents to be evaluated as an integer expression. It's a syntax element of the shell.
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
add a comment |
Use ++%n to start the counter from 0 (MyDevice_0)
PROGRAM="/bin/sh -c 'echo $((++%n))'", SYMLINK+="MyDevice_%c"
answered Jan 18 at 13:34
PooSHPooSH
111
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to usePROGRAMat all to start with 0 since you can simply use%n
– PooSH
Jan 20 at 8:04
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
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active
oldest
votes
Use the udev rules PROGRAM field to execute a /bin/sh echo expression and capture the result using %c, like this...
PROGRAM="/bin/sh -c 'echo $((%n+1))'", SYMLINK+="MyDevice_%c"
The resulting symlink will have the equivalent of MyDevice_$((%n+1)) or MyDevice_1 if %n is zero. The $(()) construct is called "arithmetic expansion" and causes the contents to be evaluated as an integer expression. It's a syntax element of the shell.
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
add a comment |
Use the udev rules PROGRAM field to execute a /bin/sh echo expression and capture the result using %c, like this...
PROGRAM="/bin/sh -c 'echo $((%n+1))'", SYMLINK+="MyDevice_%c"
The resulting symlink will have the equivalent of MyDevice_$((%n+1)) or MyDevice_1 if %n is zero. The $(()) construct is called "arithmetic expansion" and causes the contents to be evaluated as an integer expression. It's a syntax element of the shell.
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
add a comment |
Use the udev rules PROGRAM field to execute a /bin/sh echo expression and capture the result using %c, like this...
PROGRAM="/bin/sh -c 'echo $((%n+1))'", SYMLINK+="MyDevice_%c"
The resulting symlink will have the equivalent of MyDevice_$((%n+1)) or MyDevice_1 if %n is zero. The $(()) construct is called "arithmetic expansion" and causes the contents to be evaluated as an integer expression. It's a syntax element of the shell.
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
Use the udev rules PROGRAM field to execute a /bin/sh echo expression and capture the result using %c, like this...
PROGRAM="/bin/sh -c 'echo $((%n+1))'", SYMLINK+="MyDevice_%c"
The resulting symlink will have the equivalent of MyDevice_$((%n+1)) or MyDevice_1 if %n is zero. The $(()) construct is called "arithmetic expansion" and causes the contents to be evaluated as an integer expression. It's a syntax element of the shell.
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
answered Jul 9 '13 at 4:56
JimFredJimFred
1,03177
1,03177
add a comment |
add a comment |
Use ++%n to start the counter from 0 (MyDevice_0)
PROGRAM="/bin/sh -c 'echo $((++%n))'", SYMLINK+="MyDevice_%c"
answered Jan 18 at 13:34
PooSHPooSH
111
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to usePROGRAMat all to start with 0 since you can simply use%n
– PooSH
Jan 20 at 8:04
add a comment |
Use ++%n to start the counter from 0 (MyDevice_0)
PROGRAM="/bin/sh -c 'echo $((++%n))'", SYMLINK+="MyDevice_%c"
answered Jan 18 at 13:34
PooSHPooSH
111
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to usePROGRAMat all to start with 0 since you can simply use%n
– PooSH
Jan 20 at 8:04
add a comment |
Use ++%n to start the counter from 0 (MyDevice_0)
PROGRAM="/bin/sh -c 'echo $((++%n))'", SYMLINK+="MyDevice_%c"
answered Jan 18 at 13:34
PooSHPooSH
111
Use ++%n to start the counter from 0 (MyDevice_0)
PROGRAM="/bin/sh -c 'echo $((++%n))'", SYMLINK+="MyDevice_%c"
answered Jan 18 at 13:34
PooSHPooSH
111
answered Jan 18 at 13:34
PooSHPooSH
111
answered Jan 18 at 13:34
PooSHPooSH
111
answered Jan 18 at 13:34
PooSHPooSH
111
111
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to usePROGRAMat all to start with 0 since you can simply use%n
– PooSH
Jan 20 at 8:04
add a comment |
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to usePROGRAMat all to start with 0 since you can simply use%n
– PooSH
Jan 20 at 8:04
2
2
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Maybe you mean "to start the counter from 1"? Starting at 0 is exactly what OP doesn't want :)
– wazoox
Jan 18 at 17:52
Oops, I misread the OP. Sorry. Yeah, there is no need to use
PROGRAM at all to start with 0 since you can simply use %n– PooSH
Jan 20 at 8:04
Oops, I misread the OP. Sorry. Yeah, there is no need to use
PROGRAM at all to start with 0 since you can simply use %n– PooSH
Jan 20 at 8:04
add a comment |
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