Final answer:
**A) Remove the file 'junk.tmp' from the directory / var /log:
To remove the file 'junk.tmp' from the directory / var /log, you can use the following command:
rm / var / log /junk.tmp
**B) Count the number of directories:
To count the number of directories in a given directory, you can use the following command:
find /path/to/directory -type d | wc -l
**C) Run the command 'firefox' and discard its error message:
To run the command 'firefox' and discard its error message, you can use the following command:
firefox 2>/dev/null
Step-by-step explanation:
**A) To remove the file 'junk.tmp' from the directory '/ var /log', you can use the following Bash pipeline:
```bash
rm /var / l og/junk.tmp
```
The 'rm' command is used to remove files, and you provide the path to the file you want to delete as an argument. In this case, the file 'junk.tmp' in the directory '/var/log' will be removed.
**B) To count the number of directories, you can use the 'find' command in combination with the 'wc' command.
Here's an example Bash pipeline:
```bash
find /path/to/directory -type d | wc -l
```
Replace '/path/to/directory' with the actual path of the directory you want to count. The 'find' command is used to search for files and directories, and the '-type d' option filters the results to only include directories. The output of 'find' is then piped (denoted by the '|' symbol) to the 'wc' command, which is used to count the lines. The '-l' option tells 'wc' to count the number of lines in the input, which corresponds to the number of directories found.
**C) To run the command 'firefox' and discard its error message, you can redirect the error output to the null device. Here's an example Bash pipeline:
```bash
firefox 2>/dev/null
```
The 'firefox' command is used to launch the Firefox web browser. The '2>' symbol redirects the error output (denoted by '2') to the null device (represented by '/dev/null'). By doing this, any error message produced by Firefox will be discarded and not displayed in the terminal.