# pamexec

Updated: 21 December 2021
Table Of Contents

## NAME

pamexec - Execute a shell command on each image in a Netpbm image stream

## SYNOPSIS

pamexec ["command"] [netpbmfile] [-check]

Minimum unique abbreviation of option is acceptable. You may use double hyphens instead of single hyphen to denote options. You may use white space in place of the equals sign to separate an option name from its value.

## DESCRIPTION

This program is part of Netpbm.

pamexec reads a Netpbm image stream as input. For each image, it runs a specified shell command and supplies the image to it as Standard Input (with a pipe).

netpbmfile is the file name of the input file, or - to indicate Standard Input. The default is Standard Input.

Many Netpbm programs understand multimage Netpbm streams themselves, so you don't need to use pamexec to run the program on the images in the stream. Ideally, all Netpbm programs would have that capability, but multi-image streams are a relatively recent invention, so older Netpbm programs just process the first image in the stream and then stop. Even many recently written Netpbm programs work that way, since the authors aren't aware of the multi-image possibility.

Another way to process a multi-image stream is to use pamsplit to explode it into multiple files, one image per file. You can then process those files.

To run your command on a subset of the images in the stream, use pampick to select the desired images from the input stream and pipe the result to pamexec.

## OPTIONS

In addition to the options common to all programs based on libnetpbm (most notably -quiet, see Common Options), pamexec recognizes the following command line option:

-check
  This causes pamexec to exit without processing any further images if the command has a nonzero exit status.

## APPLICATIONS

To make an animated GIF movie:

        pamexec pamtogif myvideo.ppm | gifsicle --multifile >myvideo.gif

## LIMITATIONS

pamexec assumes all commands consume all of Standard Input. If yours doesn't (perhaps it just exits when it's seen enough), you can buffer through a temporary file like this, which copies the first 3 lines of every image (the PPM header) to Standard Output:

        pamexec "cat >/tmp/x; head --lines=3 x" myvideo.ppm

## HISTORY

pamexec was new in Netpbm 10.56 (September 2011).

Michael Pot wrote it, borrowing from pamsplit.

## SEE ALSO

pamfile, pampick, pamsplit, pnm, pam, cat man page

## Table Of Contents

- SYNOPSIS
- DESCRIPTION
- OPTIONS
- APPLICATIONS
- LIMITATIONS
- HISTORY
- SEE ALSO