Deepak Prasad

Bash patterns to remove an element from an array, drop the first item, dedupe (bash array remove duplicates), and subtract all values of one array from another using loops or an associative map.

Onboarding-style Bash: read usernames from a file, create multiple Linux users with useradd, optional custom shell and home under /home, per-user passwords with chpasswd, force change on first login, and test with su or …

Build a bash progress bar and bash loading bar in the terminal with carriage return redraws, reusable functions, multi-step jobs, plus pv for pipe byte counts and dialog for a gauge widget.

Count how many times a word or substring appears in a file, count lines and words with wc, whole-word matches with grep -E, and build a frequency table with awk or sort/uniq.

Find top CPU and memory consuming processes on Linux with ps, top, sar, and pidstat; sample output after controlled stress; Bash scripts that append metrics to a file and ideas for email alerts.

Bash patterns to see if a string contains a substring or character, if it is only digits, if it starts with a prefix, and how [[ =~ ]] and globs differ— with quoting, empty-string gotchas, and a short locale note.

Linux and Bash ways to check if a process is running, if a PID still exists, and how to stop a second copy of the same shell script—using kill -0, pidof, pgrep, and flock with sane lock files and cleanup.

Bash while loops: `while`/`do`/`done`, any command as the condition, `while true` with `break` and `continue`, `while read` over files, do-while style with `while true`, nested loops, and `break` vs `exit`.

Bash script arguments and bash script parameters with $0–$9, $#, "$@", shift, and a while/case example; missing-flag values, $# checks, and links to getopts and forwarding all args.

Bash check if file exists with [[ -f ]], test -e, and [ ]; bash if file exists patterns with if/else; symlinks and broken links; check if file exists on Linux with find and stat; quoting, exit codes, and pitfalls.

Bashrc vs bash_profile and profile vs bashrc: when Bash reads ~/.bashrc, ~/.bash_profile, and ~/.profile on login and new terminals, Debian vs Red Hat patterns, and what /etc/skel ships for new users.

Bash until vs while using exit status: bash until loop runs while a command fails, while loop bash runs while it succeeds. Examples for counters, wait until ready, and while read line-by-line.

Bash multiple arguments with positional parameters, bash pass all arguments via "$@", bash pass multiple arguments to a function, forwarding to another script, and bash pass function over SSH with typeset -f or declare …

Bash increment variable and bash add 1 to variable with $(( )), ((++)), bash increment variable in loop (for/while), bash increment counter patterns, let, and post vs pre-increment pitfalls.

Bash if else and bash if then else with elif chains, if else in bash shell scripts, combining conditions, nested if, exit-status semantics, and [[ ]] vs [ ] with links to string and number comparisons.

Bash getopts tutorial: optstring, OPTARG, OPTIND, opterr, bash getopts leading colon behavior for missing option arguments vs invalid options, bash getopts example scripts, shift after parsing, and getopt bash vs getopts …

Bash define function with name() or function keyword, bash function example calls, bash script function arguments ($1, $@), local vs global variables, return exit codes, and capturing output.

Bash for loop and for loop in bash: iterate words, arrays with "${a[@]}", C-style for ((i=0;i

Bash concatenate strings and bash string concat with ${a}${b}, bash append to string using +=, join strings with separators, brace pitfalls (${var}_), loops, newlines, and printf-based joining.

Bash string comparison with == and !=, bash if string equals patterns, compare strings in bash using [[ ]] and [ ], ASCII order, empty (-z) and non-empty (-n) checks, quoting, case folding, and =~ regex.

Bash compare numbers and integers with -eq, -lt, -gt, bash compare variable to number in [[ ]] and (( )), bash if numeric comparison patterns, test, loops, and pitfalls (leading zeros, floats, string vs numeric).

Bash format number with commas using printf thousands grouping, LC_NUMERIC and GNU numfmt, plus a pure Bash comma formatter for integers and decimals. Covers locale (en_US vs en_IN), C/POSIX limits, and readable output …

Nested loops in Java: nested for, while, and do-while (including mixed loops), Scanner menu example, labeled break, and complexity. Runnable examples with OpenJDK 17-tested output.

Learn how to reset index in pandas on a DataFrame or Series. Covers pandas groupby reset_index, reset index to start at 0 with drop=True, dataframe reset_index after sort or filter, df reset_index, and resetting column …

Learn how to check sudo access in Linux. Check if you or another user has sudo privileges with sudo -l, test sudo access non-interactively in a bash script with sudo -n, and list all sudo users, with real tested output.

Learn how to check disk space in Linux from the command line. Use df to check free space, du to check disk usage by folder, and find what is eating your storage, with real tested output and fixes for "No space left on …

Learn how to use git remote set-url to change a remote repository URL. Change origin from HTTPS to SSH, add or delete push URLs, rename remotes, and fix the "this repository moved" error, with real tested examples and …

Learn how to use git push force safely. Understand git push --force vs --force-with-lease, force push to a remote branch, origin master, and after rebase or amend with real examples.

Understand CPU, processor, socket, core, thread, hyper-threading, CPU cache, frequency scaling and Linux commands like lscpu, nproc, mpstat and cpupower with validated output.

Learn how to check filesystem type in Linux for mounted paths, disks, partitions, LVM volumes, USB drives, ISO media, and unmounted filesystem images with tested findmnt, lsblk, blkid, df, file, stat, udevadm, fstab, …