Pablo Iranzo Gómez, Pedro Ibáñez Requena, Miguel Pérez Colino, Scott McCarty - Red Hat Enterprise Linux 9 Administration-Packt Publishing (2022) -chap 3 82 - 180
games, initramfs, iscsi, kdump, logrotate, misc, mlocate, NetworkManager, os-prober, PackageKit, plymouth, polkit- 1, private, rhsm, rpm, rpm-state, rsyslog, samba, selinux, setroubleshoot, smartmontools, sss, systemd, tpm2-tss, udisks2, unbound, xfsdump The /root/var-files.txt file now contains both the comma-separated list for var and for /var/lib. Now, we can try to list a non-existing directory to see an error being printed: [root@rhel-instance ]# ls -m /non ls: cannot access 'non No such file or directory The output we see is an error and is treated differently by the system than regular messages. We can try to redirect the output to a file: [root@rhel-instance ]# ls -m non > non-listing.txt ls: cannot access 'non No such file or directory [root@rhel-instance ]# cat non-listing.txt [root@rhel-instance ]# We can see that using the standard redirect, with a command providing an error message, will show the error message (via STDERR) onscreen and create an empty file. This is because the file contains the output of the common information messages that are shown via STDOUT. We can still capture the output of the error, redirecting STDERR, by using 2>: [root@rhel-instance ]# ls -m/non 2> /root/error.txt [root@rhel-instance ]# cat /root/error.txt ls: cannot access 'non No such file or directory Now, we can redirect the standard output and the error output independently.
Basic Commands and Simple Shell Scripts 80 Now, we want to count the number of files and directories in var. For that, we are going to use the wc command, which stands for word count, with thew option to only focus on counting words. To do so, we will redirect the output of ls to it by using a pipe represented by |: [root@rhel-instance ]# ls -m var | wc -w
