topic Re: awk help PLEASE in Operating System - HP-UX

awk help PLEASE

David Gwin_1 — Thu, 24 Feb 2005 17:45:56 GMT

You know... I THOUGHT that I was pretty good at programming in awk until THIS!!! And maybe I just don't know the right function.

Anyhow, all I'm trying to do is determine if a file already exists. I read that the "ls /Backups" command (or any getline cmd) will only execute ONE time (I was thinking that it would execute once for each input record, WRONG).

My real question is... How do i determine if a file already exist without getting an error or system error.

BEGIN { }
{
x=0
while ("ls /Backups" | getline fl)
{
print fl " == " $1 " and x is " x
if ( test fl == $1 ) x=1
}
if (x == 0)
{
print x
system("mkdir /Backups/" $1 )
}
}

THANK YOU
David

Re: awk help PLEASE

A. Clay Stephenson — Thu, 24 Feb 2005 17:57:23 GMT

Use a variation on this theme (the key is redirecting stderr so you don'tt see any errors):

{
x = 0
while ((x < 1) && "ls /Backups 2>/dev/null" | getline fl)
{
++x
}
if (x < 1)
{
print "File not found"
}
else
{
print "File found"
}
}

Re: awk help PLEASE

David Gwin_1 — Thu, 24 Feb 2005 18:17:39 GMT

Not there... The line
while ("ls /Backups" | getline fl)
ONLY happens one time for each input file. The problem is when there is more than one line in an input file.

The actual error that I'm trying to avoid is on system mkdir command. Although it works without displaying an error, I'm not too thrilled with
system("mkdir /Backups/" $1 " 2>/dev/null")

Re: awk help PLEASE

c_51 — Thu, 24 Feb 2005 18:33:26 GMT

to test for the directory

you could do:

a=system("test -d /tmp");

a=0 if there is a directory /tmp
a!=0 if there isn't

Re: awk help PLEASE

c_51 — Thu, 24 Feb 2005 18:36:56 GMT

and to read everyline for every line of input, do something like this:

while (( "ls /tmp" | getline def ) > 0 ) {
print def;
}
close("ls /tmp");

Re: awk help PLEASE

Hein van den Heuvel — Thu, 24 Feb 2005 23:28:34 GMT

I perl you'd do somehting like:

perl -e '$dir = "/Backups/$name"; mkdir ($dir,0777) unless (-d $dir)'

fwiw,
Hein.

Re: awk help PLEASE

Muthukumar_5 — Fri, 25 Feb 2005 02:21:28 GMT

To make this simply with shell we can do as,

[[ ! -d muthu ]] && mkdir muthu

To do with AWK using your style then,

--- test. awk ---
BEGIN { }
{
x=0
while ("[[ -d muthu ]] && ls muthu"| getline fl)
{
print fl " == " $1 " and x is " x
if ( test fl == $1 ) x=1
}
}
END {
if (x == 0)
{
print x
system("mkdir muthu")
}
}

# awk -f test.awk
0
#

That is all.

Problem you had,

1. Try to do check and create new directory in the END part only.

HTH.

Re: awk help PLEASE

Gordon Morrison — Fri, 25 Feb 2005 04:42:39 GMT

Why be AWKward? ksh will do it:

if [[ -d /Backups ]]
then
echo "Directory /Backups exists"
fi

if [[ -a /Backups/filename ]]
then
echo "filename exists"
fi