Reading ls -l

What this is. Every file records who is allowed to do what with it. ls -l shows that as a ten character string at the start of each line, and it looks like noise until you know it is four fields joined together.

-rwxr-xr--

The first character is the kind: - for a file, d for a directory.

The next three are what the owner may do.

The next three are the group.

The final three are everyone else.

Reading the nine bits

A SCRIPT

-rwxr-xr--

-    ordinary file
rwx  owner: read write execute
r-x  group: read and execute
r--  others: read only

A DIRECTORY

drwxr-xr-x

d    a directory
rwx  owner: full access
r-x  group: enter and list
r-x  others: enter and list

Compare → The letters are always in the same order, r then w then x, and a dash means that permission is absent. Once you see it as three groups of three, the string reads left to right as owner, group, everyone.

✦ Execute means something different on a directory

On a file, x means this can be run as a program. On a directory, x means you may enter it and reach things inside. A directory with r but not x lets you list the names but not open anything within, which produces genuinely confusing permission denied errors on files that look perfectly readable.

SANKOFA SANDBOX

learner:~$

Try it → Run `ls -l` in your home directory, then `ls -l scripts`. Compare the first character on the directory lines with the file lines, and notice which entries have an x.

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Next: chmod, and Why Scripts Need +x →

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