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Add grep exercise #746

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a998879
Fixes to concept tree
meatball133 Dec 6, 2024
ca5f72c
Merge branch 'exercism:main' into main
meatball133 Jan 1, 2026
31aa5b6
Merge branch 'exercism:main' into main
meatball133 Jan 3, 2026
1e521ec
Add Grep exercise with implementation and tests
meatball133 Jan 3, 2026
760ddba
Implement Grep search functionality with support for flags and file h…
meatball133 Jan 3, 2026
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13 changes: 12 additions & 1 deletion bin/test-exercises.sh
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Expand Up @@ -7,10 +7,21 @@ echo $(crystal -v)
test_run() {
echo "Testing $1"
cat "$1/.meta/src/$2.cr" > "${dic}/src/$2.cr"
if [ -d "$1/assets/." ]; then
cp -a "$1/assets/." "./assets/"
fi
spec_file="$1/$(jq -r '.files.test[0]' $1/.meta/config.json)"
cat "${spec_file}" > "${dic}/spec/spec.cr"
sed -i -e 's/pending/it/g' ${dic}/spec/spec.cr
crystal spec ${dic}/spec/spec.cr || exit 1
crystal spec ${dic}/spec/spec.cr
code=$?
if [ -d "$1/assets/." ]; then
rm -rf ./assets/
fi
if [ $code -ne 0 ]; then
echo "Tests failed for $1"
exit $code
fi
}

for exercise in ./exercises/practice/*; do
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8 changes: 8 additions & 0 deletions config.json
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Expand Up @@ -1265,6 +1265,14 @@
"prerequisites": [],
"difficulty": 4
},
{
"slug": "grep",
"name": "Grep",
"uuid": "de1af862-3118-428e-8590-72806a700780",
"practices": [],
"prerequisites": [],
"difficulty": 4
},
{
"slug": "complex-numbers",
"name": "Complex Numbers",
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27 changes: 27 additions & 0 deletions exercises/practice/grep/.docs/instructions.md
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# Instructions

Search files for lines matching a search string and return all matching lines.

The Unix [`grep`][grep] command searches files for lines that match a regular expression.
Your task is to implement a simplified `grep` command, which supports searching for fixed strings.

The `grep` command takes three arguments:

1. The string to search for.
2. Zero or more flags for customizing the command's behavior.
3. One or more files to search in.

It then reads the contents of the specified files (in the order specified), finds the lines that contain the search string, and finally returns those lines in the order in which they were found.
When searching in multiple files, each matching line is prepended by the file name and a colon (':').

## Flags

The `grep` command supports the following flags:

- `-n` Prepend the line number and a colon (':') to each line in the output, placing the number after the filename (if present).
- `-l` Output only the names of the files that contain at least one matching line.
- `-i` Match using a case-insensitive comparison.
- `-v` Invert the program -- collect all lines that fail to match.
- `-x` Search only for lines where the search string matches the entire line.

[grep]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html
24 changes: 24 additions & 0 deletions exercises/practice/grep/.meta/config.json
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{
"authors": [
"meatball133"
],
"files": {
"solution": [
"src/grep.cr"
],
"test": [
"spec/grep_spec.cr"
],
"example": [
".meta/src/example.cr"
],
"editor": [
"assets/iliad.txt",
"assets/midsummer-night.txt",
"assets/paradise-lost.txt"
]
},
"blurb": "Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.",
"source": "Conversation with Nate Foster.",
"source_url": "https://www.cs.cornell.edu/Courses/cs3110/2014sp/hw/0/ps0.pdf"
}
46 changes: 46 additions & 0 deletions exercises/practice/grep/.meta/src/example.cr
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module Grep
def self.search(pattern : String, flags : Array(String), files : Array(String)) : String
# - `-n` Prepend the line number and a colon (':') to each line in the output, placing the number after the filename (if present).
# - `-l` Output only the names of the files that contain at least one matching line.
# - `-i` Match using a case-insensitive comparison.
# - `-v` Invert the program -- collect all lines that fail to match.
# - `-x` Search only for lines where the search string matches the entire line.

results = [] of String
files.each do |file|
File.open("assets/#{file}") do |f|
f.each_line.with_index(1) do |line, line_number|
line_to_check = line.chomp
pattern_to_check = pattern.dup

if flags.includes?("-i")
line_to_check = line_to_check.downcase
pattern_to_check = pattern_to_check.downcase
end

is_match = if flags.includes?("-x")
line_to_check == pattern_to_check
else
line_to_check.includes?(pattern_to_check)
end

is_match = !is_match if flags.includes?("-v")

if is_match
if flags.includes?("-l")
results << file unless results.includes?(file)
break
else
result_line = ""
result_line += "#{file}:" if files.size > 1 && !flags.includes?("-l")
result_line += "#{line_number}:" if flags.includes?("-n")
result_line += line.chomp
results << result_line
end
end
end
end
end
results.join("\n")
end
end
17 changes: 17 additions & 0 deletions exercises/practice/grep/.meta/test_template.ecr
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require "spec"
require "../src/*"

describe "<%-= to_capitalized(@json["exercise"].to_s) %>" do
<%- @json["cases"].as_a.each do |cases| %>
<%- cases["cases"].as_a.each do |subcases| %>
<%= status()%> "<%-= subcases["description"] %>" do
expected = "<%= subcases["expected"].as_a.join("\n") %>"
pattern = "<%= subcases["input"]["pattern"] %>"
flags = <%= to_s_deep(subcases["input"]["flags"]) %> <%= to_s_deep(subcases["input"]["flags"]) == "[]" ? "of String" : "" %>
files = <%= to_s_deep(subcases["input"]["files"]) %>

<%= to_capitalized(@json["exercise"].to_s) %>.search(pattern, flags, files).should eq(expected)
end
<% end %>
<% end %>
end
85 changes: 85 additions & 0 deletions exercises/practice/grep/.meta/tests.toml
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# This is an auto-generated file.
#
# Regenerating this file via `configlet sync` will:
# - Recreate every `description` key/value pair
# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
# - Preserve any other key/value pair
#
# As user-added comments (using the # character) will be removed when this file
# is regenerated, comments can be added via a `comment` key.

[9049fdfd-53a7-4480-a390-375203837d09]
description = "Test grepping a single file -> One file, one match, no flags"

[76519cce-98e3-46cd-b287-aac31b1d77d6]
description = "Test grepping a single file -> One file, one match, print line numbers flag"

[af0b6d3c-e0e8-475e-a112-c0fc10a1eb30]
description = "Test grepping a single file -> One file, one match, case-insensitive flag"

[ff7af839-d1b8-4856-a53e-99283579b672]
description = "Test grepping a single file -> One file, one match, print file names flag"

[8625238a-720c-4a16-81f2-924ec8e222cb]
description = "Test grepping a single file -> One file, one match, match entire lines flag"

[2a6266b3-a60f-475c-a5f5-f5008a717d3e]
description = "Test grepping a single file -> One file, one match, multiple flags"

[842222da-32e8-4646-89df-0d38220f77a1]
description = "Test grepping a single file -> One file, several matches, no flags"

[4d84f45f-a1d8-4c2e-a00e-0b292233828c]
description = "Test grepping a single file -> One file, several matches, print line numbers flag"

[0a483b66-315b-45f5-bc85-3ce353a22539]
description = "Test grepping a single file -> One file, several matches, match entire lines flag"

[3d2ca86a-edd7-494c-8938-8eeed1c61cfa]
description = "Test grepping a single file -> One file, several matches, case-insensitive flag"

[1f52001f-f224-4521-9456-11120cad4432]
description = "Test grepping a single file -> One file, several matches, inverted flag"

[7a6ede7f-7dd5-4364-8bf8-0697c53a09fe]
description = "Test grepping a single file -> One file, no matches, various flags"

[3d3dfc23-8f2a-4e34-abd6-7b7d140291dc]
description = "Test grepping a single file -> One file, one match, file flag takes precedence over line flag"

[87b21b24-b788-4d6e-a68b-7afe9ca141fe]
description = "Test grepping a single file -> One file, several matches, inverted and match entire lines flags"

[ba496a23-6149-41c6-a027-28064ed533e5]
description = "Test grepping multiples files at once -> Multiple files, one match, no flags"

[4539bd36-6daa-4bc3-8e45-051f69f5aa95]
description = "Test grepping multiples files at once -> Multiple files, several matches, no flags"

[9fb4cc67-78e2-4761-8e6b-a4b57aba1938]
description = "Test grepping multiples files at once -> Multiple files, several matches, print line numbers flag"

[aeee1ef3-93c7-4cd5-af10-876f8c9ccc73]
description = "Test grepping multiples files at once -> Multiple files, one match, print file names flag"

[d69f3606-7d15-4ddf-89ae-01df198e6b6c]
description = "Test grepping multiples files at once -> Multiple files, several matches, case-insensitive flag"

[82ef739d-6701-4086-b911-007d1a3deb21]
description = "Test grepping multiples files at once -> Multiple files, several matches, inverted flag"

[77b2eb07-2921-4ea0-8971-7636b44f5d29]
description = "Test grepping multiples files at once -> Multiple files, one match, match entire lines flag"

[e53a2842-55bb-4078-9bb5-04ac38929989]
description = "Test grepping multiples files at once -> Multiple files, one match, multiple flags"

[9c4f7f9a-a555-4e32-bb06-4b8f8869b2cb]
description = "Test grepping multiples files at once -> Multiple files, no matches, various flags"

[ba5a540d-bffd-481b-bd0c-d9a30f225e01]
description = "Test grepping multiples files at once -> Multiple files, several matches, file flag takes precedence over line number flag"

[ff406330-2f0b-4b17-9ee4-4b71c31dd6d2]
description = "Test grepping multiples files at once -> Multiple files, several matches, inverted and match entire lines flags"
9 changes: 9 additions & 0 deletions exercises/practice/grep/assets/iliad.txt
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Achilles sing, O Goddess! Peleus' son;
His wrath pernicious, who ten thousand woes
Caused to Achaia's host, sent many a soul
Illustrious into Ades premature,
And Heroes gave (so stood the will of Jove)
To dogs and to all ravening fowls a prey,
When fierce dispute had separated once
The noble Chief Achilles from the son
Of Atreus, Agamemnon, King of men.
7 changes: 7 additions & 0 deletions exercises/practice/grep/assets/midsummer-night.txt
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I do entreat your grace to pardon me.
I know not by what power I am made bold,
Nor how it may concern my modesty,
In such a presence here to plead my thoughts;
But I beseech your grace that I may know
The worst that may befall me in this case,
If I refuse to wed Demetrius.
8 changes: 8 additions & 0 deletions exercises/practice/grep/assets/paradise-lost.txt
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Of Mans First Disobedience, and the Fruit
Of that Forbidden Tree, whose mortal tast
Brought Death into the World, and all our woe,
With loss of Eden, till one greater Man
Restore us, and regain the blissful Seat,
Sing Heav'nly Muse, that on the secret top
Of Oreb, or of Sinai, didst inspire
That Shepherd, who first taught the chosen Seed
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