Destroyed SC2181 tell inverting return value will overwrite it (markdown)

SC2181-tell-inverting-return-value-will-overwrite-it.md

@@ -1,44 +0,0 @@
-## Check exit code directly with e.g. 'if mycmd;', not indirectly with $?.
-
-### Problematic code:
-
-```sh
-make mytarget
-
-if [ $? -ne 0 ]
-then
-  echo "Build failed"
-fi
-```
-
-### Correct code:
-
-```sh
-if ! make mytarget
-then
-  echo "Build failed"
-fi
-```
-### Rationale:
-
-Running a command and then checking its exit status `$?` against 0 is redundant.
-
-Instead of just checking the exit code of a command, it checks the exit code of a command (e.g. `[`) that checks the exit code of a command.
-
-Apart from the redundancy, there are other reasons to avoid this pattern:
-
-* Since the command and its status test are decoupled, inserting an innocent command like `echo "make finished"` after `make` will cause the `if` statement to silently start comparing `echo`'s status instead.
-* Scripts that run or are called with `set -e ` aka `errexit` will exit immediately if the command fails, even though they're followed by a clause that handles failure. 
-* The value of `$?` is overwritten by `[`/`[[`, so you can't get the original value in the relevant then/else block (e.g. `if mycmd; then echo "Success"; else echo "Failed with $?"; fi`).
-
-To check that a command returns success, use `if mycommand; then ...`.
-
-To check that a command returns failure, use `if ! mycommand; then ...`. Notice that `!` will overwrite `$?` value.
-
-To additionally capture output with command substitution: `if output=$(mycommand); then ...`
-
-This also applies to `while`/`until` loops.
-
-### Exceptions:
-
-The default Solaris 10 bourne shell does not support '!' outside of the test command (`if ! mycommand; then ...` returns `!: not found`)