From 490baffcaa9c3b032be98d69ef61b78bbbe26f96 Mon Sep 17 00:00:00 2001
From: koalaman <vidar@vidarholen.net>
Date: Sat, 1 Oct 2016 14:18:46 -0700
Subject: [PATCH] Created SC1014 (markdown)

---
 SC1014.md | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
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+## Use 'if cmd; then ..' to check exit code, or 'if [\[ $(cmd) == .. ]]' to check output.
+
+### Problematic code:
+
+```sh
+if [ grep -q pattern file ]
+then
+  echo "Found a match"
+fi
+```
+
+### Correct code:
+
+```sh
+if grep -q pattern file
+then
+  echo "Found a match"
+fi
+
+```
+### Rationale:
+
+`[ .. ]` is not part of shell syntax like `if` statements. It is not equivalent to parentheses in C-like languages, `if (foo) { bar; }`, and should not be wrapped around commands to test. 
+
+`[` is just regular command, like `whoami` or `grep`, but with a funny name (see `ls -l /bin/[`). It's a shorthand for `test`. 
+
+If you want to check the exit status of a certain command, use that command directly as demonstrated in the correct code.
+
+If you want to check the output of a command, use `"$(..)"` to get its output, and then use `test` or  `[`/`[[` to do a string comparison:
+
+```
+# Check output of `whoami` against the string `root`
+if [ "$(whoami)" = "root" ]
+then
+  echo "Running as root"
+fi
+```
+
+For more information, see [this problem in the Bash Pitfall](http://mywiki.wooledge.org/BashPitfalls#if_.5Bgrep_foo_myfile.5D) list, or generally [Test and Conditionals](http://mywiki.wooledge.org/BashGuide/TestsAndConditionals) in the WoolEdge BashGuide 
+
+### Exceptions:
+
+None.
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