From d36797bd0e85bed076f40ae3c9cae4ded9dd9d05 Mon Sep 17 00:00:00 2001
From: Vidar Holen <vidar@vidarholen.net>
Date: Tue, 8 Apr 2025 10:22:01 -0700
Subject: [PATCH] Created SC2331 (markdown)

---
 SC2331.md | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 SC2331.md

diff --git a/SC2331.md b/SC2331.md
new file mode 100644
index 0000000..eda843a
--- /dev/null
+++ b/SC2331.md
@@ -0,0 +1,34 @@
+## For file existence, prefer standard -e over legacy -a.
+
+### Problematic code:
+
+```sh
+if [ -a ~/.bash_aliases ]
+then
+  source ~/.bash_aliases
+fi
+```
+
+### Correct code:
+
+```sh
+if [ -e ~/.bash_aliases ]
+then
+  source ~/.bash_aliases
+fi
+```
+### Rationale:
+
+The POSIX standard way to check whether a file exists is `[ -e file ]`.
+
+Bash and Ksh have historically allowed using `-a`, but this has no benefit and some potential downsides. For example, in Bash `[ -a file ]` is true when the file exists, but `[ ! -a file ]` is also true, and unconditionally so, because `-a` is treated as logical "and" between non-empty strings.
+
+Avoid the ambiguity entirely by always using the standard, portable `-e`.
+
+### Exceptions:
+
+None
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!
\ No newline at end of file