Pass contents of LaTeX statement to command

Question

I can extract the contents of all the \include statements from a latex file (and append ".tex" to each one) with

grep -P "\\\\include{" Thesis_master.tex |sed -n -e"s/\\\\include{/$1/" -e" s/}.*$/.tex/p"

(I couldn't get lookbehinds working in grep, hence the pipe through sed. That gives me a list of filenames, one per line. I'd now like to pass those files to aspell. But aspell only accepts one filename as an argument, so I can't just tack |xargs aspell -c on the end.

I've read this related question but that reads from a file line by line through xargs. So how do I get it to read from the output of sed line by line?

If you show your input data then probably we can suggest lookbehind also — anubhava, Mar 28 '14 at 19:38
@anubhava, thank you: a sample line is `\include{chap_theory/chap_theory}%` I think the opening `{` was causing much of the trouble - should I or shouldn't I escape it and if so how? I tried quite a few things before just piping through sed - which I'd need to do to append the ".tex" I think — Chris H, Mar 28 '14 at 19:59
For lookbehind, use `grep -P` with perl regular expression. (assuming GNU grep) — glenn jackman, Mar 28 '14 at 20:14
@glennjackman thank you, I think I did but now can't find those attempts in my command history to check - I was probably doing something else wrong. — Chris H, Mar 28 '14 at 20:47
So the lookbehind works now but of course `grep` (by default) prints the whole line. — Chris H, Mar 28 '14 at 20:50
Then add `-o` option to grep, that only outputs the matched text — glenn jackman, Mar 28 '14 at 22:19

Digital Trauma · Accepted Answer · 2014-03-28T20:44:28.580

1

I think xargs -L 1 should do what you need:

grep -P "\\\\include{" Thesis_master.tex | \
sed -n -e"s/\\\\include{/$1/" -e" s/}.*$/.tex/p" | \
xargs -L 1 aspell -c

_{(Backslash line continuation added for readability)}

This will cause xargs to call aspell exactly once per line from the sed pipe.

Since your aspell commands appear to exit with a 255 code, this causes xargs to stop. You could trick xargs into not exiting by doing something like:

grep -P "\\\\include{" Thesis_master.tex | \
sed -n -e"s/\\\\include{/$1/" -e" s/}.*$/.tex/p" | \
xargs -L 1 -I % bash -c "aspell -c %; true"

This will run aspell in a subshell, followed by the true command which always return a 0 exit code to xargs.

edited Mar 28 '14 at 20:44

answered Mar 28 '14 at 19:19

Digital Trauma

15,475
3
51
83

I believe you're right - now trying to fix an issue with aspell closing with exit code 255 and no error message! – Chris H Mar 28 '14 at 19:59
You can debug `xargs` commands by changing your command to something like `xargs -L 1 echo aspell -c`. That way, xargs will effectively simply echo every command instead of executing it. You can then run the echoed commands manually and figure out why they're failing. – Digital Trauma Mar 28 '14 at 20:01
I was just trying that -- thanks -- I get `aspell -c chap_Theory/chap_Theory.tex` etc. Which works if I copy and paste or retype but not from xargs. Equally if I redirect the output of sed in my Q to a file tmp.txt, strip that to one line, and `cat tmp.txt | xargs aspell -c` it gives the same behaviour - I think I might have aspell related digging to do. – Chris H Mar 28 '14 at 20:05
From the `xargs` manpage: "The xargs utility exits immediately (without processing any further input) if [...], or an invocation of utility exits with a value of 255." – Digital Trauma Mar 28 '14 at 20:16
@ChrisH See my edit for a possible way to prevent xargs from quitting early – Digital Trauma Mar 28 '14 at 20:24
That didn't work either it echoes what I'd expect but with the echo taken out it gives me back the input line straight away, with some disk activity - I never see the aspell screen. But if I run `grep -P "\\\\include{" Thesis_master.tex |sed -n -e"s/\\\\include{//" -e" s/}.*$/.tex/p" |xargs -t -L 1 -I% xterm -e "aspell -c %; true"` (-t for debug) it works, just with aspell in an xterm window. Strange but I have something tat runs for now so thank you for all your help. – Chris H Mar 28 '14 at 20:39
@ChrisH Oops, I should have taken that `echo` out. Edited. – Digital Trauma Mar 28 '14 at 20:44
I thought it was there for debugging! But I think aspell is fussy about screen or I/O or something - calling xterm as in my previous comment turns out not to need the `; true`. – Chris H Mar 28 '14 at 20:53

score 1 · Answer 2 · answered Mar 28 '14 at 22:28

1

The grep recipe is:

grep -oP '\\include{\K.+?(?=})' latex.file | xargs aspell ...

answered Mar 28 '14 at 22:28

glenn jackman

238,783
38
220
352

`\K` was new to me - it seems much easier than lookbehind where it does the job. – Chris H Mar 29 '14 at 07:14
Especially when you need variable width lookbehind, which `(?<=` does not allow – glenn jackman Mar 29 '14 at 11:10

Pass contents of LaTeX statement to command

2 Answers2