Sams Teach Yourself Shell Programming in 24 Hours, Second Edition

Shell Tracing

There are many instances when syntax checking will give your script a clean bill of health, even though bugs are still lurking within it. Running syntax checking on a shell script is similar to running a spelling checker on a text document—it might find most of the misspellings, but it can't fix problems like read spelled red. In order to find and fix these types of errors in a text document, you need to proofread it. Shell tracing is proofreading your shell script.

In shell tracing mode each command is printed in the exact form that it is executed. For this reason, shell tracing mode is often referred to as execution tracing mode. Shell tracing is enabled by the -x option (x as in execution). The following command enables tracing ...