using cat to get a list to for in sh or in ksh

In article <bob-AA757D.15320506022008 RemoveThis @news.verizon.net>,
Robert Peirce <bob RemoveThis @peirce-family.com.invalid> wrote:

> In article <bob-A81B29.15162506022008 RemoveThis @news.verizon.net>,
> Robert Peirce <bob RemoveThis @peirce-family.com.invalid> wrote:
>
> > In sh and ksh, I have used
> >
> > for i in `cat file`
> > do
> > do-something-with-$i
> > done
> >
> > on other systems with no problem. In OS X, this sometimes hangs, but
> > sometimes it doesn't, which is very confusing. Pr also hangs, but for
> > some strange reason, head works in the same script!
> >
> > Does anybody have any idea what I am doing wrong? This should always
> > work fine, but sometimes it doesn't.
>
> Okay. I have more info. There seems to be some sort of buffer
> limitation in for. Perhaps somebody can tell me what it is. The file,
> in the case that hangs, is 1,635,888 lines and 24,538,320 characters.
> Other platforms seem to be able to handle this. OS X is hanging.

This is embarrassing (for OS X), but I ran this script using ksh in Uwin
on a PC and it worked:

for i in $(cat s.p); do print $i; done | head

but it doesn't work in ksh on OS X.

Cat works fine by itself, so the limitation is in the for;do;done loop.

--
Robert B. Peirce, Venetia, PA 724-941-6883
bob AT peirce-family.com [Mac]
rbp AT cooksonpeirce.com [Office]
 >> Stay informed about: using cat to get a list to for in sh or in ksh 

Robert Peirce <bob.DeleteThis@peirce-family.com.invalid> writes:

>In sh and ksh, I have used

> for i in `cat file`
> do
> do-something-with-$i
> done

>on other systems with no problem. In OS X, this sometimes hangs, but
>sometimes it doesn't, which is very confusing. Pr also hangs, but for
>some strange reason, head works in the same script!

Reading the whole file into one line exceeds the shell's line length
limit.

It works on other systems because they have longer line-length limits.
It's still a bad idea.

head(1) works because it's not reading the whole file.

The ksh(1) input mechanism is the read builtin, not cat(1). RTFM
ksh(1).

--
dhs spencer.DeleteThis@panix.com
 >> Stay informed about: using cat to get a list to for in sh or in ksh 

In article <bob-A81B29.15162506022008 DeleteThis @news.verizon.net>,
Robert Peirce <bob DeleteThis @peirce-family.com.invalid> wrote:

> In sh and ksh, I have used
>
> for i in `cat file`
> do
> do-something-with-$i
> done
>
> on other systems with no problem. In OS X, this sometimes hangs, but
> sometimes it doesn't, which is very confusing. Pr also hangs, but for
> some strange reason, head works in the same script!
>
> Does anybody have any idea what I am doing wrong? This should always
> work fine, but sometimes it doesn't.

May I suggest

while read line
do
do-something-with-$line
done <file

This will do something similar, assuming there is one item per
line.

if you have multiple fixed items per line you can do

while read item1 item2 item3
do
do-something-with-$item1
do-something-with-$item2
do-something-with-$item3
done <file

Or if you do not know how may items are on each line you can try

while read line
do
set -- $line
for item
do
do-something-with-$item
done
done <file

Bob Harris
 >> Stay informed about: using cat to get a list to for in sh or in ksh 

Bob Harris <nospam.News.Bob RemoveThis @remove.Smith-Harris.us> writes:

> while read line
> do
> set -- $line
> for item
> do
> do-something-with-$item
> done
> done <file

tr -s '[:space:]' '\n' <file |
while read x
do command $x
done

--
dhs spencer RemoveThis @panix.com
 >> Stay informed about: using cat to get a list to for in sh or in ksh 

In article <fodebg$c4t$1@reader2.panix.com>,
David Spencer <spencer DeleteThis @panix.com> wrote:

> Robert Peirce <bob DeleteThis @peirce-family.com.invalid> writes:
>
> >In sh and ksh, I have used
>
> > for i in `cat file`
> > do
> > do-something-with-$i
> > done
>
> >on other systems with no problem. In OS X, this sometimes hangs, but
> >sometimes it doesn't, which is very confusing. Pr also hangs, but for
> >some strange reason, head works in the same script!
>
> Reading the whole file into one line exceeds the shell's line length
> limit.
>
> It works on other systems because they have longer line-length limits.
> It's still a bad idea.
>
> head(1) works because it's not reading the whole file.
>
> The ksh(1) input mechanism is the read builtin, not cat(1). RTFM
> ksh(1).

I am familiar with read and I have used it in more recent scripts. This
is an old one I thought would work and it didn't. As a stopgap, I used
split to break it into smaller files that I could read with cat until I
get around to using read.

--
Robert B. Peirce, Venetia, PA 724-941-6883
bob AT peirce-family.com [Mac]
rbp AT cooksonpeirce.com [Office]
 >> Stay informed about: using cat to get a list to for in sh or in ksh