Using multitail (with examples)

Tail all files matching a pattern in a single stream

Command: multitail -Q 1 'pattern'

Motivation: This use case is helpful when you have multiple log files that you want to monitor simultaneously, but you only want to view the lines that match a specific pattern. It saves you the hassle of manually searching through each file separately.

Explanation:

• -Q 1: This option sets the quoting mode to 1, which means that the pattern will be treated as a regex pattern for filtering log lines.
• 'pattern': Replace this with the desired pattern or regular expression that you want to match in the log files.

Example output:

Log file 1:
...
matched line 1
...
matched line 2
...

Log file 2:
...
matched line 1
...
matched line 2
...

Tail all files in a directory in a single stream

Command: multitail -Q 1 'path/to/directory/*'

Motivation: This use case is useful when you have a directory containing multiple log files that you want to monitor in a single stream. It allows you to easily keep track of all the log file updates without having to open each file individually.

Explanation:

• -Q 1: Sets the quoting mode to 1 for regex pattern matching.
• 'path/to/directory/*': Replace this with the path to the directory and the wildcard * to match all files in that directory.

Example output:

Log file 1:
...
log line 1
...
log line 2
...

Log file 2:
...
log line 1
...

Automatically add new files to a window

Command: multitail -Q pattern

Motivation: This use case is helpful when you have a log file that gets rotated or replaced periodically. Instead of manually adding the new log file to the window, multitail can automatically detect the new file based on a pattern and add it to the stream.

Explanation:

• -Q pattern: Sets the quoting mode to pattern, allowing multitail to automatically add new files matching the specified pattern.
• pattern: Replace this with the pattern that matches the desired log file(s) to be automatically added. For example, if your log files have a naming convention like app.log, app.log.1, app.log.2, etc., you can specify 'app.log*' as the pattern.

Example output:

Log file 1:
...
log line 1
...
log line 2
...

Log file 2:
...
log line 1
...
log line 2
...

New log file added:
...
log line 1
...
log line 2
...

Show 5 log files while merging 2 and put them in 2 columns with only one in the left column

Command: multitail -s 2 -sn 1,3 mergefile -I file1 file2 file3 file4

Motivation: This use case is useful when you want to monitor multiple log files simultaneously while organizing them in columns. It allows you to keep track of different log files without cluttering the terminal.

Explanation:

• -s 2: Divides the screen into 2 columns.
• -sn 1,3: Specifies which log files should be shown in the left column. In this example, log files 1 and 3 will be displayed in the left column.
• mergefile: Specifies that the second column will display the merged contents of the specified log files.
• -I: This option is used to indicate that the following log file names should be treated as input files and not as patterns.

Example output:

Left column:
Log file 1:
...
log line 1
...
log line 2
...

Log file 3:
...
log line 1
...
log line 2
...

Right column (Merged log files):
...
log line 1 (from file2)
...
log line 2 (from file2)
...
log line 1 (from file4)
...
log line 2 (from file4)
...