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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

- BB


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