Update command existence check function

Credit:
* Stackoverflow: Check if a program exists from a Bash script
  Credit: https://stackoverflow.com/a/677212/4856091

2 files changed, 7 insertions, 2 deletions

diff --git a/_profile b/_profile
index 9eda66f..c71bd0b 100644
--- a/_profile
+++ b/_profile
@@ -31,8 +31,9 @@ _path_append() {
 }
 
 ## Check the existence/accessibility of a command
+# Credit: https://stackoverflow.com/a/677212/4856091
 _exists() {
-    which $1 &> /dev/null
+    command -v "$1" >/dev/null 2>&1
 }
 
 ## Check whether the program is running
diff --git a/_zsh/40-functions.zsh b/_zsh/40-functions.zsh
index 77db01c..2b078ed 100644
--- a/_zsh/40-functions.zsh
+++ b/_zsh/40-functions.zsh
@@ -5,8 +5,12 @@
 #
 
 ## Check the existence/accessibility of a command
+# Credit: https://stackoverflow.com/a/677212/4856091
 function exists() {
-    which $1 &> /dev/null
+    # 'command' is POSIX-compliant and more portable;
+    # 'hash' only searches for commands;
+    # while 'type' also considers builtins and keywords.
+    type "$1" >/dev/null 2>&1
 }
 
 ## Check whether the program is running