[module]
name = "wc"
description = "Count lines, words, and characters in files"
version = 1
[intro]
text = """
## What is wc?
`wc` (word count) counts lines, words, and bytes/characters in files or standard input.
## Basic Syntax
```
wc [OPTIONS] [FILE...]
```
## Common Flags
- `-l` — count lines only
- `-w` — count words only
- `-c` — count bytes
- `-m` — count characters (respects multibyte/UTF-8)
- (no flag) — print lines, words, and bytes together
## Tips
- `wc -l < file.txt` — redirect instead of passing filename suppresses the filename in output
- Pipe output through `tr -d ' '` to strip leading spaces (BSD `wc` adds them)
- `wc` is useful in pipelines: `grep 'error' log.txt | wc -l`
"""
[[examples]]
title = "Count lines"
description = "Print the number of lines in a file"
command = "wc -l < notes.txt"
output = "3\n"
[[examples]]
title = "Count words"
description = "Print the number of words in a file"
command = "wc -w < notes.txt"
output = "9\n"
[[examples]]
title = "Count in a pipeline"
description = "Count how many error lines are in a log file"
command = "grep 'ERROR' app.log | wc -l | tr -d ' '"
output = "2\n"
[[exercises]]
id = "wc.1"
difficulty = "beginner"
question = """The file `words.txt` has one word per line.
Count the number of lines in it."""
expected_output = "5\n"
hints = [
"Use wc -l with input redirection to suppress the filename",
"Try: wc -l < words.txt | tr -d ' '",
]
solution = "wc -l < words.txt | tr -d ' '"
match_mode = "exact"
[[exercises.fixtures]]
filename = "words.txt"
content = "apple\nbanana\ncherry\ndate\nelderberry\n"
[[exercises]]
id = "wc.2"
difficulty = "beginner"
question = """The file `sentence.txt` contains a sentence.
Count the number of words in it."""
expected_output = "6\n"
hints = [
"Use wc -w with input redirection",
"Try: wc -w < sentence.txt | tr -d ' '",
]
solution = "wc -w < sentence.txt | tr -d ' '"
match_mode = "exact"
[[exercises.fixtures]]
filename = "sentence.txt"
content = "the quick brown fox jumps high\n"
[[exercises]]
id = "wc.3"
difficulty = "beginner"
question = """The file `log.txt` has log entries.
Count only the lines that contain the word 'ERROR'."""
expected_output = "3\n"
hints = [
"Pipe grep output into wc -l",
"Try: grep 'ERROR' log.txt | wc -l | tr -d ' '",
]
solution = "grep 'ERROR' log.txt | wc -l | tr -d ' '"
match_mode = "exact"
[[exercises.fixtures]]
filename = "log.txt"
content = "INFO: started\nERROR: disk full\nINFO: ok\nERROR: timeout\nWARN: slow\nERROR: crash\n"
[[exercises]]
id = "wc.4"
difficulty = "intermediate"
question = """The file `data.txt` has text.
Print the number of words and the number of lines, separated by a space, in that order."""
expected_output = "8 4\n"
hints = [
"Run wc with both -w and -l flags and use awk to reformat",
"Try: wc -wl < data.txt | awk '{print $2, $1}'",
]
solution = "wc -wl < data.txt | awk '{print $2, $1}'"
match_mode = "exact"
[[exercises.fixtures]]
filename = "data.txt"
content = "one two\nthree four\nfive six\nseven eight\n"
[[exercises]]
id = "wc.5"
difficulty = "intermediate"
question = """The directory has two text files: `a.txt` (3 lines) and `b.txt` (5 lines).
Find the total number of lines across all .txt files using find and xargs."""
expected_output = "8\n"
hints = [
"Pipe find output into xargs wc -l, then extract the total line",
"Try: find . -name '*.txt' | xargs wc -l | tail -1 | awk '{print $1}' | tr -d ' '",
]
solution = "find . -name '*.txt' | xargs wc -l | tail -1 | awk '{print $1}' | tr -d ' '"
match_mode = "exact"
[[exercises.fixtures]]
filename = "a.txt"
content = "line1\nline2\nline3\n"
[[exercises.fixtures]]
filename = "b.txt"
content = "line1\nline2\nline3\nline4\nline5\n"
[[exercises]]
id = "wc.6"
difficulty = "advanced"
question = """The file `data.txt` has text spread across three lines with three words each.
Print three numbers on one line: line count, word count, byte count (space-separated)."""
expected_output = "3 9 18\n"
hints = [
"wc with no flags prints all three counts; use awk to strip the filename",
"Try: wc < data.txt | awk '{print $1, $2, $3}'",
]
solution = "wc < data.txt | awk '{print $1, $2, $3}'"
match_mode = "exact"
[[exercises.fixtures]]
filename = "data.txt"
content = "a b c\nd e f\ng h i\n"