Shell man if

[balanga]

I thought (mistakenly) that I would be be able to understand this code if I ran man if

if [ -r /etc/defaults/periodic.conf ]
then
    . /etc/defaults/periodic.conf
    source_periodic_confs
fi

but I can't, so can someone help me out?

 

[SirDice]

That will lead you to builtin(1) because it's a shell builtin. This means it's going to be different between various shells. In this case it's sh(1) because all system scripts use that shell. It's not going to explain how this works though. This explains it better: https://www.grymoire.com/Unix/Sh.html#uh-76

Bookmark this site: https://www.grymoire.com/Unix/Sh.html

 

[covacat]

man test
for [] syntax

 

[SirDice]

Annotated:

if [ -r /etc/defaults/periodic.conf ]   # checks if the file /etc/defaults/periodic.conf exists and is readable
then
    . /etc/defaults/periodic.conf       # if it is readable, source the file
    source_periodic_confs               # execute a function that's defined in /etc/defaults/periodic.conf
fi