feeding a series of input args to a command that only takes one

Sometimes I have commands that are designed only to process a single
input argument but I want to call them repeatedly on a list.

For example I generate a command line pipe that outputs a list of ip
addresses:

cmd1 | cmd2 | tr '\n' '\t'

11.0.0.21 11.0.0.176 11.0.0.191

To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
<ip address>

Is there a command line metaphor to feed a command one arg at a time
repeatedly. I guess I could use a for loop but that's somewhat unweildly
on the command line.

--
Rahul

On 2008-05-01, Rahul <nospam@nospam.invalid> wrote:
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
><ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.

man xargs

--keith

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Rahul wrote:
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
> <ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>
Assuming your "cmd1 | cmd2" pipe above outputs a single IP address
per line, try:

cmd1 | cmd2 | xargs --max-args=1 ip2hex


Regards,

Kees.

--
Kees Theunissen

Kees Theunissen <theuniss@rijnh.nl> wrote in
news:481a2703$0$14343$e4fe514c@news.xs4all.nl:

> Assuming your "cmd1 | cmd2" pipe above outputs a single IP address
> per line, try:
>
> cmd1 | cmd2 | xargs --max-args=1 ip2hex

Thanks Kees and Keith. That's perfect. I had tried xargs before I posted
but did not realize the --max-args option was what I needed!

--
Rahul

Rahul wrote:
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
> <ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>

xargs -n 1

See 'man xargs' for details.

Janis

On 2008-05-01, Rahul <nospam@nospam.invalid> wrote:
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
><ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>

xargs has the -n flag to control how many arguments it uses at a time;
it spawns as many instances of the program as necessary to use up all
the arguments:

other_stuff | xargs -n 1 ip2hex

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On 2008-05-01, Rahul <nospam@nospam.invalid> wrote:
>
>
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
><ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>
while read ip_address

On Thu, 01 May 2008 20:06:21 +0000, Rahul wrote:

> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
> <ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.

cmd1 | cmd2 | while read ip ; do ip2hex $ip ; done

does not look too bad to me.

On May 1, 4:06*pm, Rahul <nos...@nospam.invalid> wrote:
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 * * * 11.0.0.176 * * *11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
> <ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>
> --
> Rahul

pipe your output thru xargs...

cmd1 | cmd2 | tr '\n' '\t' | xargs -l ip2hex

On May 1, 4:06 pm, Rahul <nos...@nospam.invalid> wrote:
> Sometimes I have commands that are designed only to process a single
> input argument but I want to call them repeatedly on a list.
>
> For example I generate a command line pipe that outputs a list of ip
> addresses:
>
> cmd1 | cmd2 | tr '\n' '\t'
>
> 11.0.0.21 11.0.0.176 11.0.0.191
>
> To convert to hex I have ip2hex that accepts only 1 arg. ip2hex: ip2hex
> <ip address>
>
> Is there a command line metaphor to feed a command one arg at a time
> repeatedly. I guess I could use a for loop but that's somewhat unweildly
> on the command line.
>
> --
> Rahul

You can use xargs -n1, which limits only one arg at a time. IIRC, this
is GNU xargs and other versions may not support it. Check it out.
Sashi