diff --git a/.idea/misc.xml b/.idea/misc.xml
index fee09bd..89e54d4 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -20,6 +20,7 @@
     <cargoProject FILE="$PROJECT_DIR$/generics/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/lifetimes/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/adder/Cargo.toml" />
+    <cargoProject FILE="$PROJECT_DIR$/minigrep/Cargo.toml" />
   </component>
   <component name="ComposerJsonPluginSettings">
     <unboundedVersionInspectionSettings>
diff --git a/.idea/rust.iml b/.idea/rust.iml
index fca239b..eb9d073 100644
--- a/.idea/rust.iml
+++ b/.idea/rust.iml
@@ -78,6 +78,10 @@
       <sourceFolder url="file://$MODULE_DIR$/adder/examples" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/adder/tests" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/adder/benches" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/minigrep/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/minigrep/examples" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/minigrep/tests" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/minigrep/benches" isTestSource="true" />
       <excludeFolder url="file://$MODULE_DIR$/adder/target" />
       <excludeFolder url="file://$MODULE_DIR$/branches/target" />
       <excludeFolder url="file://$MODULE_DIR$/ctof/target" />
@@ -89,6 +93,7 @@
       <excludeFolder url="file://$MODULE_DIR$/guessing_game/target" />
       <excludeFolder url="file://$MODULE_DIR$/lifetimes/target" />
       <excludeFolder url="file://$MODULE_DIR$/loops/target" />
+      <excludeFolder url="file://$MODULE_DIR$/minigrep/target" />
       <excludeFolder url="file://$MODULE_DIR$/modules/target" />
       <excludeFolder url="file://$MODULE_DIR$/rectangles/target" />
       <excludeFolder url="file://$MODULE_DIR$/references/target" />
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index fed1dab..54a3b77 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -14,45 +14,29 @@
   </component>
   <component name="FileEditorManager">
     <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
-      <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/adder/src/lib.rs">
-          <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="1025">
-              <caret line="66" column="5" selection-start-line="66" selection-start-column="5" selection-end-line="66" selection-end-column="5" />
-              <folding>
-                <element signature="e#251#252#0" expanded="true" />
-                <element signature="e#263#264#0" expanded="true" />
-                <element signature="e#304#305#0" expanded="true" />
-                <element signature="e#338#339#0" expanded="true" />
-                <element signature="e#1036#1037#0" expanded="true" />
-                <element signature="e#1077#1078#0" expanded="true" />
-                <element signature="e#1119#1120#0" expanded="true" />
-                <element signature="e#1160#1161#0" expanded="true" />
-                <element signature="e#1196#1197#0" expanded="true" />
-                <element signature="e#1241#1242#0" expanded="true" />
-                <element signature="e#1191#1192#0" expanded="true" />
-                <element signature="e#1232#1233#0" expanded="true" />
-                <element signature="e#1520#1521#0" expanded="true" />
-                <element signature="e#1551#1552#0" expanded="true" />
-              </folding>
-            </state>
-          </provider>
-        </entry>
-      </file>
       <file pinned="false" current-in-tab="true">
-        <entry file="file://$PROJECT_DIR$/adder/tests/integration_test.rs">
+        <entry file="file://$PROJECT_DIR$/minigrep/src/main.rs">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="96">
-              <caret line="6" column="20" selection-start-line="6" selection-start-column="20" selection-end-line="6" selection-end-column="20" />
+            <state relative-caret-position="320">
+              <caret line="20" lean-forward="true" selection-start-line="20" selection-end-line="20" />
             </state>
           </provider>
         </entry>
       </file>
       <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/adder/tests/common/mod.rs">
+        <entry file="file://$PROJECT_DIR$/minigrep/src/lib.rs">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="48">
-              <caret line="3" lean-forward="true" selection-start-line="3" selection-end-line="3" />
+            <state relative-caret-position="517">
+              <caret line="33" column="6" selection-start-line="33" selection-start-column="6" selection-end-line="33" selection-end-column="6" />
+            </state>
+          </provider>
+        </entry>
+      </file>
+      <file pinned="false" current-in-tab="false">
+        <entry file="file://$PROJECT_DIR$/minigrep/poem.txt">
+          <provider selected="true" editor-type-id="text-editor">
+            <state relative-caret-position="128">
+              <caret line="8" column="19" selection-start-line="8" selection-start-column="19" selection-end-line="8" selection-end-column="19" />
             </state>
           </provider>
         </entry>
@@ -110,6 +94,9 @@
         <option value="$PROJECT_DIR$/adder/src/lib.rs" />
         <option value="$PROJECT_DIR$/adder/tests/common/mod.rs" />
         <option value="$PROJECT_DIR$/adder/tests/integration_test.rs" />
+        <option value="$PROJECT_DIR$/minigrep/poem.txt" />
+        <option value="$PROJECT_DIR$/minigrep/src/lib.rs" />
+        <option value="$PROJECT_DIR$/minigrep/src/main.rs" />
       </list>
     </option>
   </component>
@@ -143,20 +130,13 @@
             <path>
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
               <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
-              <item name="adder" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+              <item name="minigrep" type="9f88c78c:ScopeViewTreeModel$FileNode" />
             </path>
             <path>
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
               <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
-              <item name="adder" type="9f88c78c:ScopeViewTreeModel$FileNode" />
-              <item name="tests" type="9f88c78c:ScopeViewTreeModel$FileNode" />
-            </path>
-            <path>
-              <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
-              <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
-              <item name="adder" type="9f88c78c:ScopeViewTreeModel$FileNode" />
-              <item name="tests" type="9f88c78c:ScopeViewTreeModel$FileNode" />
-              <item name="common" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+              <item name="minigrep" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+              <item name="src" type="9f88c78c:ScopeViewTreeModel$FileNode" />
             </path>
           </expand>
           <select />
@@ -189,7 +169,7 @@
   </component>
   <component name="PropertiesComponent">
     <property name="JavaScriptWeakerCompletionTypeGuess" value="true" />
-    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1548965323798" />
+    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1548969593161" />
     <property name="javascript.nodejs.core.library.configured.version" value="7.1.0" />
     <property name="js.eslint.eslintPackage" value="$USER_HOME$/.yarn-config/global/node_modules/.bin/eslint" />
     <property name="js.eslint.nodeInterpreter" value="project" />
@@ -327,8 +307,8 @@
     <frame x="1680" y="-410" width="1050" height="1657" extended-state="6" />
     <editor active="true" />
     <layout>
-      <window_info active="true" content_ui="combo" id="Project" order="0" sideWeight="0.49663138" visible="true" weight="0.26141885" />
-      <window_info id="Structure" order="1" sideWeight="0.5033686" side_tool="true" visible="true" weight="0.26141885" />
+      <window_info content_ui="combo" id="Project" order="0" sideWeight="0.49710983" visible="true" weight="0.26141885" />
+      <window_info id="Structure" order="1" sideWeight="0.50289017" side_tool="true" visible="true" weight="0.26141885" />
       <window_info id="Image Layers" order="2" />
       <window_info id="Designer" order="3" />
       <window_info id="Capture Tool" order="4" />
@@ -344,7 +324,7 @@
       <window_info anchor="bottom" id="Docker" order="7" show_stripe_button="false" />
       <window_info anchor="bottom" id="Version Control" order="8" />
       <window_info anchor="bottom" id="Inspection Results" order="9" weight="0.32979318" />
-      <window_info anchor="bottom" id="Terminal" order="10" visible="true" weight="0.32924467" />
+      <window_info active="true" anchor="bottom" id="Terminal" order="10" visible="true" weight="0.32989025" />
       <window_info anchor="bottom" id="Event Log" order="11" side_tool="true" />
       <window_info anchor="right" id="Commander" order="0" weight="0.4" />
       <window_info anchor="right" id="Ant Build" order="1" weight="0.25" />
@@ -589,9 +569,23 @@
         </state>
       </provider>
     </entry>
+    <entry file="file://$PROJECT_DIR$/adder/tests/common/mod.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="48">
+          <caret line="3" lean-forward="true" selection-start-line="3" selection-end-line="3" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/adder/tests/integration_test.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="144">
+          <caret line="9" lean-forward="true" selection-start-line="9" selection-end-line="9" />
+        </state>
+      </provider>
+    </entry>
     <entry file="file://$PROJECT_DIR$/adder/src/lib.rs">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="1025">
+        <state relative-caret-position="1056">
           <caret line="66" column="5" selection-start-line="66" selection-start-column="5" selection-end-line="66" selection-end-column="5" />
           <folding>
             <element signature="e#251#252#0" expanded="true" />
@@ -612,17 +606,24 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/adder/tests/common/mod.rs">
+    <entry file="file://$PROJECT_DIR$/minigrep/poem.txt">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="48">
-          <caret line="3" lean-forward="true" selection-start-line="3" selection-end-line="3" />
+        <state relative-caret-position="128">
+          <caret line="8" column="19" selection-start-line="8" selection-start-column="19" selection-end-line="8" selection-end-column="19" />
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/adder/tests/integration_test.rs">
+    <entry file="file://$PROJECT_DIR$/minigrep/src/lib.rs">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="96">
-          <caret line="6" column="20" selection-start-line="6" selection-start-column="20" selection-end-line="6" selection-end-column="20" />
+        <state relative-caret-position="517">
+          <caret line="33" column="6" selection-start-line="33" selection-start-column="6" selection-end-line="33" selection-end-column="6" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/minigrep/src/main.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="320">
+          <caret line="20" lean-forward="true" selection-start-line="20" selection-end-line="20" />
         </state>
       </provider>
     </entry>
diff --git a/minigrep/Cargo.toml b/minigrep/Cargo.toml
new file mode 100644
index 0000000..de54896
--- /dev/null
+++ b/minigrep/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "minigrep"
+version = "0.1.0"
+authors = ["Timothy Warren <twarren@nabancard.com>"]
+edition = "2018"
+
+[dependencies]
diff --git a/minigrep/poem.txt b/minigrep/poem.txt
new file mode 100644
index 0000000..8707527
--- /dev/null
+++ b/minigrep/poem.txt
@@ -0,0 +1,9 @@
+I'm nobody! Who are you?
+Are you nobody, too?
+Then there's a pair of us - don't tell!
+They'd banish us, you know.
+
+How dreary to be somebody!
+How public, like a frog
+To tell your name the livelong day
+To an admiring bog!
diff --git a/minigrep/src/lib.rs b/minigrep/src/lib.rs
new file mode 100644
index 0000000..64ed7a9
--- /dev/null
+++ b/minigrep/src/lib.rs
@@ -0,0 +1,101 @@
+use std::env;
+use std::error::Error;
+use std::fs;
+
+pub struct Config {
+    pub query: String,
+    pub filename: String,
+    pub case_sensitive: bool,
+}
+
+impl Config {
+    pub fn new(args: &[String]) -> Result<Config, &'static str> {
+        if args.len() < 3 {
+            return Err("not enough arguments");
+        }
+
+        let query = args[1].clone();
+        let filename = args[2].clone();
+
+        let case_sensitive = env::var("CASE_INSENSITIVE").is_err();
+
+        Ok(Config { query, filename, case_sensitive })
+    }
+}
+
+pub fn run(config: Config) -> Result<(), Box<dyn Error>> {
+    // The ? operator passes the error back to the caller.
+    let contents = fs::read_to_string(config.filename)?;
+
+    let results = if config.case_sensitive {
+        search(&config.query, &contents)
+    } else {
+        search_case_insensitive(&config.query, &contents)
+    };
+
+    for line in results {
+        println!("{}", line);
+    }
+
+    Ok(())
+}
+
+fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
+    let mut results = Vec::new();
+
+    for line in contents.lines() {
+        if line.contains(query) {
+            results.push(line)
+        }
+    }
+
+    results
+}
+
+fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
+    let query = query.to_lowercase();
+    let mut results = Vec::new();
+
+    for line in contents.lines() {
+        if line.to_lowercase().contains(&query) {
+            results.push(line)
+        }
+    }
+
+    results
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn case_sensitive() {
+        let query = "duct";
+        let contents = "\
+Rust:
+safe, fast, productive.
+Pick three.
+Duct tape.";
+
+        assert_eq!(
+            vec!["safe, fast, productive."],
+            search(query, contents)
+        );
+    }
+
+    #[test]
+    fn case_insensitive() {
+        let query = "rUsT";
+        let contents = "\
+Rust:
+safe, fast, productive.
+Pick three.
+Trust me.";
+
+        assert_eq!(
+            vec!["Rust:", "Trust me."],
+            search_case_insensitive(query, contents)
+        );
+    }
+}
diff --git a/minigrep/src/main.rs b/minigrep/src/main.rs
new file mode 100644
index 0000000..8302095
--- /dev/null
+++ b/minigrep/src/main.rs
@@ -0,0 +1,20 @@
+use std::env;
+use std::process;
+
+use minigrep;
+use minigrep::Config;
+
+fn main() {
+    // collect turns an iterator into a collection
+    let args: Vec<String> = env::args().collect();
+
+    let config = Config::new(&args).unwrap_or_else(|err| {
+        eprintln!("Problem parsing arguments: {}", err);
+        process::exit(1);
+    });
+
+    if let Err(e) = minigrep::run(config) {
+        eprintln!("Application error: {}", e);
+        process::exit(1);
+    }
+}