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Shell

182 problems12 sections📅 2026 curriculum

Learn shell scripting by typing real commands.

Type your way to shell fluency: pipelines, variables and quoting, conditionals and loops, parameter expansion, and the command substitution that glues tools together. Each snippet is real Bash, and an AI tutor explains every line — why quoting a variable prevents word splitting, how a pipe streams data between commands — so the terminal stops feeling like guesswork as you build speed.

Progress0 / 182 solved · 0/12 sections

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Run Shell on your machine

1. Install the toolchain

bash ships with macOS/Linux

2. Save your code as script.sh, then compile & run

bash script.sh # or: chmod +x script.sh && ./script.sh

Official install docs ↗

progress by section

1Fundamentals0/17start →

Comments echo Shebang Variables and assignment Single vs double quotes Integer arithmetic Command substitution Exit status printf Reading a variable Environment variables Escaping let Positional parameters Special variables Local variables in functions Strict mode

2Strings In Depth0/17start →

Concatenation String length Lowercase Uppercase Contains a substring Extract fields with cut Default value Replace all matches Replace first match Substring Translate with tr Strip a prefix Padding with printf Repeat a string Strip a suffix Split on a delimiter Trim whitespace

3Text Processing0/18start →

grep basics head and tail wc -l and -w awk print columns cut -d -f sed substitute s///g sort, numeric, reverse column -t align grep -i, -v, -c tee split output tr translate and delete uniq and uniq -c awk running sum grep -E extended regex sed delete and print awk -F and patterns paste columns together comm compare sorted

4File I/O0/14Unlock →

read a file with cat count lines in a file create with touch write with > and >>here-document <<EOF here-string <<<temp file with mktemp test file existence combine streams with &>read a file into a variable redirect stderr with 2>read line by line process a file line by line read a file into an array

5Networking0/20Unlock →

6Commands0/14Unlock →

run a command exit code $?pipe with |chain with && and ||command substitution $(...)which and command -v env vars for one command grouping { ...; }xargs build arguments background & and wait subshell (...)timeout a command trap on EXIT and INT getopts parse flags

7Conditionals0/14Unlock →

if / elif / else && and ||[[ ]] test Numeric tests [ ] POSIX test String tests case statement File tests case with patterns Branch on exit status Ternary-ish with && / ||Nested conditions Regex match [[ =~ ]]Regex capture groups

8Loops0/14Unlock →

for over a list for over a range while loop break continue Loop with a counter for over an array until loop C-style for ((;;))for over a glob Infinite loop with break Nested loops Loop over command output while read line

9Functions0/14Unlock →

Define a function Arguments $1 and $@Default argument local variables Validate argument count Capture output with $()Function with a loop return status vs echo exit vs return Passing an array shift Sourcing a library Recursion getopts option parsing

10Arrays0/14Unlock →

Declare an array Index into an array Expand all elements Append to an array Iterate an array Array length Associative arrays Delete an element Array indices Read into an array Slice an array Iterate a map Join with a separator mapfile into an array

11Parameter Expansion0/14Unlock →

Length Tilde expansion Arithmetic expansion Command substitution Brace expansion Case conversion Quote removal Substring Parameter defaults Search and replace Globbing and extglob Pattern removal Indirect expansion Process substitution

12Pipelines0/12Unlock →

a simple pipe pipeline output to a file counting with wc multi-stage pipeline tee inside a pipe sort then head (top-N)xargs from a pipe grep then awk pipeline into while read pipefail process substitution named pipe with mkfifo