diff --git a/README.md b/README.md
index 68ad4d6ab..06c2a5494 100644
--- a/README.md
+++ b/README.md
@@ -101,7 +101,7 @@ Result 1 out of 1:
 ----------------------------------------------------
 ```
 
-#### stdin
+#### Input
 
 Normalize an expression using a ruleset (See [Rulesets](#rulesets)).
 Read the expression from stdin.
@@ -120,6 +120,11 @@ Result 1 out of 1:
 ----------------------------------------------------
 ```
 
+Alternatively, the path to the file containing a Phi expression can be passed as a positional argument:
+```sh
+stack run -- --rules-yaml ./eo-phi-normalizer/test/eo/phi/rules/yegor.yaml test.phi
+```
+
 #### `--chain`
 
 Use `--chain` to see numbered normalization steps for each normalization result.
@@ -151,6 +156,14 @@ stack run -- --single --rules-yaml ./eo-phi-normalizer/test/eo/phi/rules/yegor.y
 ⟦ a ↦ ξ.b (c ↦ ⟦ ⟧).d (ρ ↦ ⟦ b ↦ ⟦ c ↦ ∅, d ↦ ⟦ φ ↦ ξ.ρ.c ⟧ ⟧ ⟧) ⟧
 ```
 
+#### Output
+
+By default, the normalization output will be printed to `stdout`.
+The `--output` CLI option (or its shorthand `-o`) can be used to specify the path to the file to which the output will be written instead.
+The file will be created if it didn't originally exist.
+
+This is equivalent to redirecting the output from `stdout` to a file using `>`.
+
 ## Rulesets
 
 A ruleset describes a set of user-defined rewriting rules.
diff --git a/eo-phi-normalizer/test/eo/phi/rules/yegor.yaml b/eo-phi-normalizer/test/eo/phi/rules/yegor.yaml
index 7f075d91b..f8e0285a5 100644
--- a/eo-phi-normalizer/test/eo/phi/rules/yegor.yaml
+++ b/eo-phi-normalizer/test/eo/phi/rules/yegor.yaml
@@ -47,11 +47,11 @@ rules:
       ⟦ !B, ρ ↦ ξ.σ ⟧
     when:
       - present_attrs:
-          attrs: ["σ"]
-          bindings: ["!B"]
+          attrs: ['σ']
+          bindings: ['!B']
       - absent_attrs:
-          attrs: ["ρ"]
-          bindings: ["!B"]
+          attrs: ['ρ']
+          bindings: ['!B']
     tests:
       - name: 'Has sigma and no rho'
         input: '⟦ b ↦ ⟦ ⟧, σ ↦ ⟦ ⟧ ⟧ '
@@ -78,7 +78,7 @@ rules:
     tests: []
 
   - name: Rule 5
-    description: "ξ-dispatch"
+    description: 'ξ-dispatch'
     context:
       current_object: ⟦ !a ↦ ξ.!b, !B ⟧
     pattern: |
@@ -89,13 +89,13 @@ rules:
     tests: []
 
   - name: Rule 6
-    description: "Accessing an α-binding"
+    description: 'Accessing an α-binding'
     pattern: |
       ⟦ !a ↦ !n, !B ⟧.!a
     result: |
       !n(ρ ↦ ⟦ !B ⟧)
     when:
-      - nf: ["!n"]
+      - nf: ['!n']
     tests:
       - name: Should match
         input: ⟦ hello ↦ ⟦⟧ ⟧.hello
@@ -103,17 +103,17 @@ rules:
         matches: true
       - name: Shouldn't match
         input: ⟦ ⟧.hello
-        output: ""
+        output: ''
         matches: false
 
   - name: Rule 7
-    description: "Application"
+    description: 'Application'
     pattern: |
       ⟦ !a ↦ ∅, !B ⟧(!a ↦ !n)
     result: |
       ⟦ !a ↦ !n, !B ⟧
     when:
-      - nf: ["!n"]
+      - nf: ['!n']
     tests: []
 
   - name: Rule 8
@@ -123,10 +123,10 @@ rules:
     result: |
       !n.!a
     when:
-      - nf: ["!n"]
+      - nf: ['!n']
       - absent_attrs:
-          attrs: ["!a"]
-          bindings: ["!B"]
+          attrs: ['!a']
+          bindings: ['!B']
     tests:
       - name: 'Attribute does not exist'
         input: '⟦ φ ↦ ⟦ ⟧, a ↦ ⟦ ⟧ ⟧.b'
@@ -138,11 +138,11 @@ rules:
         matches: false
 
   - name: Rule 9
-    description: "Parent application"
+    description: 'Parent application'
     pattern: ⟦ ρ ↦ !t, !B ⟧(ρ ↦ !n)
     result: ⟦ ρ ↦ !n, !B ⟧
     when:
-      - nf: ["!n"]
+      - nf: ['!n']
     tests: []
 
   - name: Rule 10
@@ -150,7 +150,7 @@ rules:
     pattern: ⟦ !t ↦ !b1, !B1 ⟧(!t ↦ !b2, !B2)
     result: ⊥
     when:
-      - not_equal: ["!t", "ρ"]
+      - not_equal: ['!t', 'ρ']
     tests:
       - name: ''
         input: '⟦ t ↦ ⟦ a ↦ ∅ ⟧ ⟧(t ↦ ⟦ b ↦ ∅ ⟧)'
@@ -165,11 +165,11 @@ rules:
       ⊥
     when:
       - absent_attrs:
-          attrs: ["!a", "φ", "λ"]
-          bindings: ["!B"]
+          attrs: ['!a', 'φ', 'λ']
+          bindings: ['!B']
       - present_attrs:
-          attrs: ["ρ", "σ"]
-          bindings: ["!B"]
+          attrs: ['ρ', 'σ']
+          bindings: ['!B']
     tests:
       - name: 'Accessing nonexistent attribute'
         input: '⟦ ρ ↦ ⟦ ⟧, σ ↦ ⟦ ⟧ ⟧.x'