TCSH / CSH: set vs setenv Command Differences

The set and setenv commands in tcsh and csh shells are used to set environment variables, but with some differences:

1. Syntax: The syntax for the set and setenv commands is different. set uses the following syntax:

set variable = value

while setenv uses the following syntax:

setenv variable value

1. Scoping: set sets a shell variable, which is only visible within the current shell and any child processes. setenv sets an environment variable, which is visible to all processes started from the current shell.
2. Export: setenv automatically exports the environment variable to the environment of child processes, while set does not. To export a shell variable to the environment, you need to use the export command in tcsh or csh.

rnFor example, to set the PATH environment variable in tcsh or csh, you can use either setenv:

setenv PATH /usr/local/bin:$PATH

or set followed by export:

set PATH = /usr/local/bin:$PATH
export PATH

In general, it is recommended to use setenv for setting environment variables and set for setting shell variables, unless you need to set a variable that should only be visible within the current shell.