8.17 verbose and echo Variables Show Quoting

The C shell has two variables (6.9 ) that, when set, will help you follow the convoluted trail of variable and metacharacter expansion. This will echo every command line before shell variables have been evaluated:

set
 

% set verbose

This command will display each line after the variables and metacharacters have been substituted:

% set echo

If you wish to turn the variables off, use unset (6.8 ) instead of set .

The Bourne shell syntax is different. To turn on the verbose flag, use:

$ set -v

The command set  -x turns on the echo flag. You can also type them together: set  -xv .

If your version of UNIX understands (44.4 ) scripts that start with #! , here's a convenient way to turn these variables on from the first line of a script:

#!/bin/sh -xv

It is not necessary to modify the program. You can enable variable tracing in Bourne shell scripts by typing the shell name and options on the command line:

$ sh -v 

script


$ sh -x 

script

Not all Bourne shells let you turn these variables off. If yours does, you can do it by using a plus sign instead of a minus sign:

set +xv