Published Book on Amazon
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All of IOT Starting with the Latest Raspberry Pi from Beginner to Advanced – Volume 1 |
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All of IOT Starting with the Latest Raspberry Pi from Beginner to Advanced – Volume 2 |
출판된 한글판 도서
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최신 라즈베리파이(Raspberry Pi)로 시작하는 사물인터넷(IOT)의 모든 것 – 초보에서 고급까지 (상) |
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최신 라즈베리파이(Raspberry Pi)로 시작하는 사물인터넷(IOT)의 모든 것 – 초보에서 고급까지 (하) |
Original Book Contents
10.5 Commands Related to Operation
10.5.1 "expr" Command – Arithmetic Operation
You can use the "expr" command to perform arithmetic operations.
[Command Format]
| expr [OPTION] / [EXPRESSION] |
[Command Overview]
■ This performs arithmetic operation on the specified operation expression.
■ User privilege -- Normal user.
[Detail Description]
■ This command basically requires spaces for operand and operator.
■ Use ` ` (backtab) to store the values computed using this command elsewhere.
■ Note that you must use escape (＼) when you use "*".
[Main Option]
| --help | display this help and exit |
| --version | output version information and exit |
[주요 expression]
| ARG1 | ARG2 | ARG1 if it is neither null nor 0, otherwise ARG2 |
| ARG1 & ARG2 | ARG1 if neither argument is null or 0, otherwise 0 |
| ARG1 < ARG2 | if ARG1 is less than ARG2, then 1, otherwise 0 |
| ARG1 <= ARG2 | if ARG1 is less than or equal to ARG2, then 1, otherwise 0 |
| ARG1 = ARG2 | if ARG1 is equal to ARG2, then 1, otherwise 0 |
| ARG1 != ARG2 | if ARG1 is unequal to ARG2, then 1, otherwise 0 |
| ARG1 >= ARG2 | if ARG1 is greater than or equal to ARG2, then 1, otherwise 0 |
| ARG1 > ARG2 | if ARG1 is greater than ARG2, then 1, otherwise 0 |
| ARG1 + ARG2 | arithmetic sum of ARG1 and ARG2 |
| ARG1 - ARG2 | arithmetic difference of ARG1 and ARG2 |
| ARG1 * ARG2 | arithmetic product of ARG1 and ARG2 |
| ARG1 / ARG2 | arithmetic quotient of ARG1 divided by ARG2 |
| ARG1 % ARG2 | arithmetic remainder of ARG1 divided by ARG2 |
[Used Example]
The followings are some of the examples that use this command
| pi@raspberrypi ~ $ echo `expr 5 + 4' |
| 9 |
| pi@raspberrypi ~ $ echo `expr 11 – 6' |
| 5 |
| pi@raspberrypi3:~ $ echo `expr 10 "|" 75` |
| 10 |
| pi@raspberrypi3:~ $ echo `expr 0 "|" 75` |
| 75 |
| pi@raspberrypi3:~ $ echo `expr 10 ">" 75` |
| 0 |
| pi@raspberrypi3:~ $ echo `expr 10 ">" 7` |
| 1 |
| pi@raspberrypi3:~ $ echo `expr 10 "<" 7` |
| 0 |
| pi@raspberrypi3:~ $ echo `expr 10 "<" 75` |
| 1 |