A Passionate Techie

curl writes the output to stderr, so redirect that and also suppress the progress: curl - v -- silent https :// google . com / 2 >& 1 | grep expire The reason why  curl  writes the information to stderr is so you can do: curl <url> | someprgram  without that information clobbering the input of  someprogram It is possible to use  --stderr -  as parameter, to redirect the output from stderr (default) to stdout. With this option you also should use  --silent  to suppress the progress bar. $ curl - v -- silent https :// google . com / -- stderr - | grep expire * expire date : 2015 - 09 - 01 00 : 00 : 00 GMT  

In this article of the shell script debugging series, we will explain the third shell script debugging mode, that is shell tracing and look at some examples to demonstrate how it works, and how it can be used. The previous part of this series clearly throws light upon the two other shell script debugging modes: verbose mode and syntax checking mode with easy-to-understand examples of how to enable shell script debugging in these modes. Shell tracing simply means tracing the execution of the commands in a shell script. To switch on shell tracing, use the -x debugging option. This directs the shell to display all commands and their arguments on the terminal as they are executed. We will use the sys_info.sh shell script below, which briefly prints your system date and time, number of users logged in and the system uptime. However, it contains syntax errors that we need to find and correct. #!/bin/bash #script to print brief system info ROOT_ID="0" DATE=`date` NO_USERS=`who |...