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53 lines
2.7 KiB
53 lines
2.7 KiB
2 years ago
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## in-back-ground
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### Instructions
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Create a script `in-back-ground.sh` which will execute a job in the background that will do the following:
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- Run the command `cat` on the file "facts" which will read the contents of the file and print it to `stdout`.
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- The output of the cat command will be piped to the `grep` command, which will search for the string `"moon"` in the file.
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- If the `grep` command succeeds ( if it finds the string "moon"), the echo command will run and print `"The moon fact was found!"` to the `output.log` file.
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- If the command finds the string "moon", it will print the matching line to the `stdout`.
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- Redirect the `stdout` to a new file `output.log`
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- Redirect `stderr` to the same place as `stdout` (in this case, the output.log file).
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You must do all these steps running only one job and using the command `nohup`!
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Expected output:
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```console
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$ ./in-back-ground.sh
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nohup: redirecting stderr to stdout
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- Australia is wider than the moon. The moon sits at 3400km in diameter, while Australia’s diameter from east to west is almost 4000km.
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$ ls
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facts in-back-ground.sh output.log
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$ cat output.log
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The moon fact was found!
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$
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```
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### Hints
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The `nohup` command is used to run a command in the background, even if you close the terminal or log out of the system. When a command is run with nohup, it ignores the "SIGHUP" signal, which is sent to processes when the terminal they are running in is closed.
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For example, to run the `ls` command in the background with `nohup`, you can use the following command:
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```console
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$ nohup ls &
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```
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This will run the "ls" command in the background, and ignore the "SIGHUP" signal. The "&" symbol puts the "ls" command in the background, allowing the terminal to continue accepting input while the "ls" command is running.
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In a Unix-like shell, stdin, stdout, and stderr are three standard streams that are used to communicate with a program or process.
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- `stdin` (standard input) is a stream of data that a program or process reads from. By default, stdin is the keyboard, but it can be redirected to read from a file or the output of another command.
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- `stdout` (standard output) is a stream of data that a program or process writes to. It can be redirected to write to a file or to the input of another command using the `>` operator.
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- `stderr` (standard error) is a stream of data that a program or process writes to for error messages and other diagnostic output. It can also be redirected to write to a file or to the input of another command using the `2>` operator.
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- In order to redirect both stdout and stderr to a file you can use the `2>&1` operator.
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> You have to use Man or Google to know more about commands flags, in order to solve this exercise!
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> Google and Man will be your friends!
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