"If" Construct in Unix Scripting

Question

I have just started writing shell scripts. In if constructs, is the if considered to be a command or a keyword?

If it is a command, its path should be listed when searched through the which command. In reality, which does not find anything.

If if is not a command then ideally it does not need to be separated by a semicolon when then is written in the same line.

Can any of you please explain whether if is a command or a statement?

It can't be an external command, because it has to affect the behavior of commands and statements that come after it in the script, and also has to match up with the fi keyword. — Barmar
– Barmar, Commented Dec 15, 2013 at 8:54

phs · Accepted Answer · 2013-12-15 08:33:52Z

1

In bash if is a compound command (see "Shell Grammar" in the linked page.)

answered Dec 15, 2013 at 8:33

phs

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3 Comments

Rob Starling Over a year ago

Yes! Please read the bash man page. It has a lot of information on scripting.

Rob Starling Over a year ago

Also, be aware of bash features that are extensions beyond what the POSIX sh (Bourne Shell) supports and mark your scripts as #!/bin/bash scripts if they require such features.

William Pursell Over a year ago

pubs.opengroup.org/onlinepubs/9699919799/utilities/…

anubhava · Accepted Answer · 2013-12-15 08:32:57Z

0

if is not a command it is the shell's construct.

Semicolon ; after condition is the shell syntax to terminate the condition and is required only when then keyword is on the same line. ; is not mandatory when then keyword appears on the next line.

So this will also work without semicolon and print date:

if ((RANDOM>0))
then
    date
fi

answered Dec 15, 2013 at 8:32

anubhava

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Comments

William Pursell · Accepted Answer · 2015-05-06 06:01:16Z

0

if is a keyword. The semi-colon terminates the command that is between if and then.

answered May 6, 2015 at 6:01

William Pursell

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