Grep/Multiple Matches

course-definition.yml

@@ -83,6 +83,14 @@ extensions:
 
       Along the way, you'll learn about extracting matched lines, formatting output, and managing line-by-line processing.
 
+  - slug: "multiple-matches"
+    name: "Multiple Matches"
+    description_markdown: |
+      In this challenge extension, you'll add support for printing the multiple matching results to your Grep implementation.
+
+      Along the way, you'll learn about how to implement the `-o` flag.
+
+
 stages:
   - slug: "cq2"
     name: "Match a literal character"
@@ -312,6 +320,7 @@ stages:
     marketing_md: |-
       In this stage, we'll add support for `{n,m}`, the [between n and m times](https://docs.microsoft.com/en-us/dotnet/standard/base-types/quantifiers-in-regular-expressions#match-between-n-and-m-times-nm) quantifier.
 
+  # Printing Matches
   - slug: "ku5"
     primary_extension_slug: "printing-matches"
     name: "Print a single matching line"
@@ -324,4 +333,26 @@ stages:
     name: "Print multiple matching lines"
     difficulty: easy
     marketing_md: |-
-      In this stage, you'll add support for printing multiple input lines if they match the pattern.
+      In this stage, you'll add support for printing multiple input lines if they match the pattern.
+
+  # Multiple matches
+  - slug: "cj0"
+    primary_extension_slug: "multiple-matches"
+    name: "Print single match"
+    difficulty: medium
+    marketing_md: |-
+      In this stage, you'll add support for printing a single matching text to your grep implementation.
+
+  - slug: "ss2"
+    primary_extension_slug: "multiple-matches"
+    name: "Print multiple matches"
+    difficulty: medium
+    marketing_md: |-
+      In this stage, you'll add support for printing multiple matching texts from a single line to your grep implementation.
+
+  - slug: "bo4"
+    primary_extension_slug: "multiple-matches"
+    name: "Process multiple input lines"
+    difficulty: medium
+    marketing_md: |-
+      In this stage, you'll add support for processing multiple input lines to print all matching texts.

stage_descriptions/multiple-matches-01-cj0.md

@@ -0,0 +1,33 @@
+In this stage, you'll add support for printing a single matching text to your grep implementation.
+
+### The `-o` flag
+
+The `-o` flag, also known as the `only-matching` flag, is used to print only the matching texts in a separate line.
+
+Example usage:
+
+```bash
+$ echo -ne "I have one cow" | grep -o -E 'cow'
+cow
+```
+
+### Tests
+
+The tester will execute your program like this:
+
+```bash
+$ echo -n "The king had 7 daughters" | ./your_program.sh -o -E "\d"
+7
+```
+
+If the input line does not match the specified pattern, your program must:
+- Exit with the code 1
+- Exit with no printed output
+
+If the input line matches the specified pattern, your program must:
+- Print the matched text to the standard output
+- Exit with the code 0
+
+### Notes
+
+- You only need to handle a single line of input and a single occurence of the pattern. We'll get to printing multiple matches and processing multiple lines in the later stages.

stage_descriptions/multiple-matches-02-ss2.md

@@ -0,0 +1,40 @@
+In this stage, you'll add support for printing multiple matching texts from a single line to your grep implementation.
+
+
+### Printing multiple matches
+
+If there are multiple matches present in the same line, each of them is printed on a separate line.
+
+```bash
+# The '\d' pattern matches 1 and 0 separately
+$ echo -n "The king had 10 children" | grep -o -P '\d'
+1
+0
+
+# The `\d\d` matches a pair of digits, so each pair (if found) is printed in its own line
+$ echo -n "The king had 10 children" | grep -o -P '\d\d'
+10
+```
+
+### Tests
+
+The tester will execute your program like this:
+
+```bash
+$ echo -e "jekyll and hyde" | ./your_program.sh -o -E "(jekyll|hyde)"
+jekyll
+hyde
+```
+
+If none of the lines match the specified pattern, your program must:
+- Exit with the code 1
+- Exit with no printed output
+
+If at least one line matches the pattern, your program must:
+
+- Exit with the code 0
+- Print all the matching parts to the standard output
+
+### Notes
+
+- You only need to handle the case of a single input line. We will get to processing multiple input lines in later stages.

stage_descriptions/multiple-matches-03-bo4.md

@@ -0,0 +1,42 @@
+In this stage, you'll add support for processing multiple input lines to print all matching texts.
+
+### Printing multiple matches from multiple lines
+
+If there are multiple lines in the input, matches from all lines are printed, each on their own line.
+
+```bash
+# The '\d' pattern matches 1 and 0 separately in multiple lines
+$ echo -ne "Line1: 10\nLine2: 42" | grep -o -P '\d'
+1
+1
+0
+2
+4
+2
+
+# The `\d\d` matches a pair of digits, so each pair (if found) is printed in its own line
+$ echo -ne "Line01: 50\nLine02: 42" | grep -o -P '\d\d'
+01
+50
+02
+42
+```
+
+### Tests
+
+The tester will execute your program like this:
+
+```bash
+$ echo -e "jekyll and hyde\nmickey mouse" | ./your_program.sh -o -E "(jekyll|hyde|mouse)"
+jekyll
+hyde
+mouse
+```
+
+If none of the lines match the specified pattern,
+- Your program should exit with the code 1
+- No output should be printed
+
+If at least one line matches the pattern,
+- Your program should exit with the code 0
+- All the matching parts from all lines should be printed on their separate lines