How Can I Use An "if" statement on a Single Command Line?

jagooch · 02-10-2009, 10:51 AM

I would like to execute some branching logic on a single command line.

So, I want to say something like:

if [ -z "`ls -A /home/autosys/archive`" ]; then; rm /home/autosys/archive/*.*;fi;

Except it doesn't work. It give me an "invalid token near 'then'" message when I run it. I've played with the semicolon near 'then' a bit and cannot get it to work. I've removed it , place it before and after the 'then' without success.

Thank You,

-TheGooch

Maligree · 02-10-2009, 10:59 AM

Too many semicolons. Try it this way:

Code:

if [ 1 == 1 ]; then echo "true"; fi

rweaver · 02-10-2009, 11:05 AM

Quote:

Originally Posted by jagooch

I would like to execute some branching logic on a single command line.

So, I want to say something like:

if [ -z "`ls -A /home/autosys/archive`" ]; then; rm /home/autosys/archive/*.*;fi;

Except it doesn't work. It give me an "invalid token near 'then'" message when I run it. I've played with the semicolon near 'then' a bit and cannot get it to work. I've removed it , place it before and after the 'then' without success.

Thank You,

-TheGooch

Basically you have some extra ;'s where they're not needed. Remove teh one after the "then" and remove the one after the "fi" and the rest should work provided its correct (I don't think that if statement does what you expect.)

Basically, each element that *requires* a line after it must have a ; otherwise it shouldn't. These are all valid as far as structure go.

Code:

if [ -z "`ls -A /home/autosys/archive`" ]; then rm /home/autosys/archive/*.*; fi

Code:

if [ -z "`ls -A /home/autosys/archive`" ]
  then 
    rm /home/autosys/archive/*.*
fi

Code:

if [ -z "`ls -A /home/autosys/archive`" ]
  then rm /home/autosys/archive/*.*
fi

Code:

if [ -z "`ls -A /home/autosys/archive`" ]; then
  rm /home/autosys/archive/*.*
fi

custangro · 02-10-2009, 06:16 PM

Quote:

Originally Posted by jagooch

I would like to execute some branching logic on a single command line.

So, I want to say something like:

if [ -z "`ls -A /home/autosys/archive`" ]; then; rm /home/autosys/archive/*.*;fi;

Except it doesn't work. It give me an "invalid token near 'then'" message when I run it. I've played with the semicolon near 'then' a bit and cannot get it to work. I've removed it , place it before and after the 'then' without success.

Thank You,

-TheGooch

Or you can...

Code:

root@host# [ -z $(ls -A /home/autosys/archive) ] && rm /home/autosys/archive/*.*

FYI...using `command` is deprecated, but if you're in a shell it's better because it's faster to type

i92guboj · 02-10-2009, 11:32 PM

Quote:

Originally Posted by custangro

Or you can...

Code:

root@host# [ -z $(ls -A /home/autosys/archive) ] && rm /home/autosys/archive/*.*

FYI...using `command` is deprecated, but if you're in a shell it's better because it's faster to type

Assuming that "archive" is a dir, which I deduct from the thread, this would suffice:

Code:

[ -a /home/autosys/archive/* ] && rm -rf /home/autosys/archive/*
# or
if [ -a /home/autosys/archive/* ]; then rm -rf /home/autosys/archive/*; fi

There's no need to throw "ls" in the middle if you are using bash. Also, check the bash man page (CONDITIONAL EXPRESSIONS) if you want to know more about this stuff. -a will check that the file exists, but maybe you want to check for -f (regular files only) and change rm -rf by rm -f... It all depends on what do you exactly need.