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Pattern Matching with grep The grep utility searches for patterns within files or directory trees. grep "error" system.log grep -i "failed" app.log # Case-insensitive matching grep -w "function" script.sh # Whole word matches only grep -e "warning" -e "alert" debug.txt # Multiple ...

Monitoring Live Log Updates with Tail The tail command is primarily used with the -f flag to monitor a file in real-time as new data is appended. -f, --follow[={name|descriptor}] Continuously display new output as the file grows. Without an argument, it defaults to 'descriptor'. Example us ...

Wildcards Shell wildcards are used for filename and directory name matching. They are processed by the shell and appear exclusively in command arguments. Wildcard Patterns Pattern Description * Matches any sequence of characters, including empty strings ? Matches exactly one character [] Matches any single character within the specif ...

Text Search and Pattern Matching The grep utility filters input streams based on regular expressions. Appending the -i flag forces case-insensitive comparisons, which is useful when parsing unstandardized logs. grep -i "authentication failed" auth.log File Discovery and Size Queries find traverses directory hierarchies and applies te ...

Regular expressions (regex) are patterns used to match character combinations in text, consisting of literal characters and metacharacters with special meanings. They enable efficient searching, extraction, and manipulation of text based on defined rules. In Linux environments, regex is intergal to commend-line utilities like grep, sed, and awk ...

Viewing and Navigating File Streams The cat utility dumps an entire file's contents directly to standard output. For large datasets requiring paginated reading, more or less provide an interactive terminal viewer. cat /etc/os-release less /etc/nginx/nginx.conf Press q inside the pager to exit cleanly. Extracting Boundary Lines head and tail st ...

Removing Blank Lines To delete all blank lines and those containing only whitespace: :g/^$/d To remove lines that contain only spaces or tabs: :g/^\\s\*$/d To eliminate lines starting with #, or with spaces or tabs followed by #: :g/^\\s\*#/d For PHP configuration files where comments start with ;: :g/^\\s\*;/d To delete lines from the second l ...

Modifying Network Interface Configuraton 1. Update the Network Configuration File Edit the configuraton file for the target interface (e.g., ens33). vim /etc/sysconfig/network-scripts/ifcfg-ens33 Adjust the following parameters: NAME=enp0 # Corresponds to net.ifnames=0 DEVICE=enp0 # Corresponds to biosdevname=0 2. Rename the Configuratio ...