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How to pass control to an external program
* How to pass over part of the source to an external program?
There are two ways, <cmd>executesystemcommand</cmd> and
<cmd>installprogram</cmd>. <cmd>executesystemcommand</cmd> is equal to
<cmd>immediate</cmd><cmd>write18</cmd> while <cmd>installprogram</cmd> defines
a program in the tui file which is then run before the next execution of
texexec. I do not know what is the best source of their documenentation.
<cmd>write</cmd> is explained in the texbook, <cmd>write18</cmd> executes its argument on shell.
luatex will have a better model for executing commands on the shell, and some
of it is explained in the luatex manual. (But luatex is still pre-alpha, so
the interface can change).
<cmd>installprogram</cmd> is not documented, you need to read cont-uti.tex and
texutil.rb to understand how it works.
I found ConTeXt sources to be the best way to understand how these things are
working. See t-lilypond, which checks if write18 is enabled or not, and then
uses <cmd>executesystemcommand</cmd> or <cmd>installprogram</cmd>. The module
writes stuff to a temporary file, and then uses lilypond to get a ps/pdf which
is included back in the document. Another example is m-r.tex which writes
things to a temp file and runs them through R (a statistical program) and
types the output. It also shows how you can capture the contents of an
evironment to a temp file. The same idea is used in the t-vim module. Of
course, the ConTeXt sources have plenty of examples. There is also core-buf
where the buffer handling is implemented, and the sources related to metapost
handling, which are perhaps the best example of how to go back and forth
between tex and an external program.
Perhaps the R module is easiest to understand. That method will work for most
cases where you simply want to capture part of tex source and write it
verbatim to a file, and then read the output back into tex.
If you want to read the output verbatim to ConTeXt, you can use
<code>\typefile{filename}</code>. If the external program outputs tex file,
then you can use <code>\input{filename}</code>.
There are two ways, <cmd>executesystemcommand</cmd> and
<cmd>installprogram</cmd>. <cmd>executesystemcommand</cmd> is equal to
<cmd>immediate</cmd><cmd>write18</cmd> while <cmd>installprogram</cmd> defines
a program in the tui file which is then run before the next execution of
texexec. I do not know what is the best source of their documenentation.
<cmd>write</cmd> is explained in the texbook, <cmd>write18</cmd> executes its argument on shell.
luatex will have a better model for executing commands on the shell, and some
of it is explained in the luatex manual. (But luatex is still pre-alpha, so
the interface can change).
<cmd>installprogram</cmd> is not documented, you need to read cont-uti.tex and
texutil.rb to understand how it works.
I found ConTeXt sources to be the best way to understand how these things are
working. See t-lilypond, which checks if write18 is enabled or not, and then
uses <cmd>executesystemcommand</cmd> or <cmd>installprogram</cmd>. The module
writes stuff to a temporary file, and then uses lilypond to get a ps/pdf which
is included back in the document. Another example is m-r.tex which writes
things to a temp file and runs them through R (a statistical program) and
types the output. It also shows how you can capture the contents of an
evironment to a temp file. The same idea is used in the t-vim module. Of
course, the ConTeXt sources have plenty of examples. There is also core-buf
where the buffer handling is implemented, and the sources related to metapost
handling, which are perhaps the best example of how to go back and forth
between tex and an external program.
Perhaps the R module is easiest to understand. That method will work for most
cases where you simply want to capture part of tex source and write it
verbatim to a file, and then read the output back into tex.
If you want to read the output verbatim to ConTeXt, you can use
<code>\typefile{filename}</code>. If the external program outputs tex file,
then you can use <code>\input{filename}</code>.
