What are the three commands to view logs in Linux?

Three commands for viewing logs in Linux: 1. To view real-time changing logs, the code is [tail -f filename]; 2. To search for logs near keywords, the code is [cat -n filename |grep " Keyword "]; 3. Enter the edit search.

The operating environment of this tutorial: windows7 system, linux7.3 version, DELL G3 computer. This method is suitable for all brands of computers.

Three commands for viewing logs in Linux:

The first one: View real-time changing logs (more memory intensive)

The most commonly used:

• tail -f filename (default last 10 lines, equivalent to adding parameter -n 10)

• Ctrl c is to exit the tail command

Other situations:

• tail -n 20 filename (Display the last 20 lines of filename)

• tail -n 5 filename (Display the file starting from line 5)

Second type: Search logs near keywords

The most commonly used:

cat -n filename |grep "keyword"

Other situations:

• ##cat filename | grep -C 5 'keyword' (display the line matching the string in the log and the 5 lines before and after)

• cat filename | grep -B 5 'Keyword' (display matching string and first 5 lines)

• cat filename | grep -A 5 'Keyword' (display matching string and the next 5 lines)

Third method: Enter the edit search:vi(vim)

1. Enter vim editing mode: vim filename

2. Enter "/keyword" and press enter to find

3. To find the next one, press "n" You can

Exit: After pressing the ESC key and then entering the : sign, vi will wait for us to enter the command

• wq at the bottom of the screen! Save and exit;

• q! Exit without saving;

Other situations:

• /Keyword Note: For forward search, press the n key to move the cursor to the next matching position

• ?Keyword Note: For reverse search, press the shift n key to move the cursor to the next matching position Conditional

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