“setenv: command not found” when running shell scripts in Bash

Environment

Operating System: Linux, macOS, or other Unix-like systems

Shells: Bash (bash), C-shell (csh), TC-shell (tcsh)

Issue

When executing a shell script using bash ./script.sh, the following error is displayed:
$ bash ./script.sh
./script.sh: line 3: setenv: command not found
The script is intended to set environment variables but fails with a “command not found” error, even though the script appears correct.

Resolution

Instead of forcing the script to run with bash, make it executable and allow the system to use the correct interpreter specified in the script’s shebang line.

Make the script executable using the chmod +x command. This grants the file permission to be executed.
```
$ chmod +x ./script.sh
```
Run the script directly. The operating system will automatically use the interpreter specified in the shebang line (e.g., #!/bin/csh).
```
$ ./script.sh
```
Note

If the script is not in your PATH, you must use a relative path (./script.sh) or an absolute path (/path/to/your/script.sh) to run it.

Root Cause

The error occurs because the script is being executed with the wrong shell interpreter.

The command setenv is used by the C-shell (csh) and TC-shell (tcsh) to define environment variables.
The command bash ./script.sh explicitly tells the system to use bash as the interpreter, ignoring the shebang line (the first line of the script, e.g., #!/bin/csh).
bash does not have a built-in setenv command. The bash equivalent is export.

For example, a script written for csh might look like this:

#!/bin/csh
# This is a csh script
setenv MY_VARIABLE "hello"
echo "My variable is $MY_VARIABLE"

When you run bash ./script.sh, bash tries to interpret setenv MY_VARIABLE “hello”, which is invalid syntax in bash, leading to the “command not found” error. By making the script executable and running it with ./script.sh, you allow the system to read the #!/bin/csh shebang and use the correct csh interpreter.

Diagnosis

You can check the first line of the script (the shebang) to identify which interpreter it is designed for.

Use the head command to view the first line of your script:
```
$ head -n 1 ./script.sh
#!/bin/csh
```
If the line starts with #!/bin/csh or #!/bin/tcsh, the script is intended for the C-shell or TC-shell, and the resolution above applies.
If it starts with #!/bin/bash, the script is a bash script, and the use of setenv is an error in the script itself. In this case, it should be replaced with export.