How to open and view a large log of 4-5 GB?

• tail -f filename.log — to view the last lines and monitor new entries in real-time.
• less filename.log — for step-by-step viewing. Allows navigation through the file (up/down, search).
• grep "pattern" filename.log — to find specific lines containing a certain pattern.
• awk '/pattern/ { print $0 }' filename.log — a more powerful tool for parsing and filtering.
• Using utilities designed for log handling: lnav, logtool.
• Splitting a file into parts using split:

  split -b 1G filename.log log_part_
  

  Then viewing the parts separately.
• Loading a part of the file:

  head -c 1G filename.log > first_gb.log
  

• Archiving: compress the file before viewing if appropriate, for example using gzip or xz, and then view through the corresponding utilities (zless, zcat).

The choice of method depends on the task: whether you need to view the entire file, search for something specific, or monitor changes.