For a long time, I’ve been naming my shell scripts with the .sh
extension and assuming they’d run just fine in any shell. Most of the time, they worked perfectly—but every now and then, I’d hit unexpected issues, especially when running them with sh scriptName.sh
.
This got me thinking: Why do we even name our scripts scriptName.sh
? Shouldn't it be scriptName.bash
if it's written specifically for Bash?
Most of my scripts begin with a shebang like this:
#!/bin/bash
This line ensures the script is executed with Bash when run directly, for example:
./scriptName.sh
However, if I run the same script with:
sh scriptName.sh
The shebang is completely ignored! Instead, the script is executed using sh
(which might point to a more basic shell like dash
on many systems). This often works fine—until the script relies on Bash-specific features.
sh
Runs a Bash Script?Here’s an example of a script that breaks when run with sh
:
#!/bin/bash
echo "Using Bash!"
my_array=(one two three)
echo "Second element: ${my_array[1]}"
Run with Bash (or Directly):
./scriptName.sh
Output:
Using Bash!
Second element: two
Run with sh
:
sh scriptName.sh
Output:
Using Bash!
scriptName.sh: 3: scriptName.sh: Syntax error: "(" unexpected
The error occurs because sh
doesn’t support arrays or other Bash-specific features. This happens because the sh
command forces the use of a simpler shell, completely ignoring the shebang.
.sh
Can Be MisleadingNaming a script scriptName.sh
implies it’s compatible with sh
(or any POSIX-compliant shell). But if your script relies on Bash-specific features, this isn’t true. This mislabeling can confuse others—or even you—into running the script incorrectly.
.bash
If a script depends on Bash, naming it with the .bash
extension might be more accurate. For example:
scriptName.bash
This naming convention immediately signals that the script is Bash-specific, reducing the likelihood of running it with sh
by mistake.
If my script starts with #!/bin/bash
, I’ll always run it using Bash:
bash scriptName.sh
sh
to ensure compatibility.Make scripts executable and run them directly:
chmod +x scriptName.sh
./scriptName.sh
.sh
only for POSIX-compliant scripts..bash
for scripts that rely on Bash-specific features.sh
, I’ll avoid Bash-only features like arrays or [[ ]]
.Understanding the difference between sh
and bash
and how the shebang works has saved me a lot of frustration. Going forward, I’ll pay closer attention to how I name and run my scripts to ensure compatibility and clarity.
What about you? Have you ever run into similar issues with .sh
scripts or interpreter mismatches? Let me know your thoughts—I’d love to hear your experiences!