Comparing Directory Name to String

bcgreen24 · 01-09-2013, 05:43 PM

Will someone PLEASE restore my sanity? I'm using this script to run a command within each subdirectory in the 'sites' directory, EXCLUDING the 'all' subdirectory. However, when I run this, the 'all' subdirectory is still being used, even though I use an if statement to exclude it.

Code:

for dir in ~/htdocs/drupal/drupal/sites/*
  do
    if [ $dir = "/local/users/drupadm/htdocs/drupal/drupal/all" ]
    then
      continue
    fi
    echo $dir
    (cd $dir && /opt/webstack/php/5.2/bin/php /local/users/drupadm/drush/drush.php $1)
  done

Thanks in advance for any and all help!

Bryan

sundialsvcs · 01-10-2013, 09:05 AM

Add a statement to echo each value of $dir to see what the value actually is. (Move the statement you've now got to the top of the loop, just for debugging purposes.

unSpawn · 01-10-2013, 09:56 AM

AFAIK "~/htdocs/drupal/" can never be "/local/users/" unless "${HOME}" is /local/users/? And don't use "for" loops but "while" ones and properly quote variables.

Code:

#!/bin/bash
# Set debug and error mode while testing, set default behaviour and there's a "$1" on line 8 so exit if it wasn't supplied:
set -vx; LANG=C; LC_ALL=C; export LANG LC_ALL; [ $# -eq 0 ] && { echo "Need one argument, exiting."; exit 1; }
find ~/htdocs/drupal/drupal/sites/* -type d | while read RESULT; do
 [ "${RESULT}" = "/local/users/drupadm/htdocs/drupal/drupal/all" ] || \
 { echo "${RESULT}"; ( cd "${RESULT}" && /opt/webstack/php/5.2/bin/php /local/users/drupadm/drush/drush.php "$1"); }
done; exit 0

theNbomr · 01-10-2013, 12:12 PM

Please explain the downside of for loops in this context. I use that pattern all the time and I don't think I've ever bumped into problems with it.
--- rod.

unSpawn · 01-10-2013, 12:45 PM

Kind of OT but here goes:

Code:

mkdir theNbomr; cd theNbomr; mkdir "Please explain"; mkdir "the downside of for loops"; mkdir "in this"; mkdir context.

\ls -1Q
"context."
"in this"
"Please explain"
"the downside of for loops"

for dir in *; do \ls -1dQ $dir; done
"context."
ls: "in": No such file or directory
ls: "this": No such file or directory
ls: "Please": No such file or directory
ls: "explain": No such file or directory
ls: "the": No such file or directory
ls: "downside": No such file or directory
ls: "of": No such file or directory
ls: "for": No such file or directory
ls: "loops": No such file or directory

find . -type d | while read ITEM; do ls -1dQ "${ITEM}"; done
"./Please explain"
"./the downside of for loops"
"./in this"
"./context."

I think one can safely say that "while" loop usage should be the default reflex unless specifically requiring a "for" loop. It's one of the BaSH pitfalls a few LQ members have educated ppl about over the past years, one of them being David the H. Apart from the ABS also see http://mywiki.wooledge.org/.

theNbomr · 01-10-2013, 03:51 PM

Yeah, I see. I'm religious about the no-whitespace-in-filenames so that partly explains why I haven't been tripped up by it. I'm also fairly likely to use

Code:

for dir in *; do \ls -1dQ "$dir"; done

which seems like a simple enough solution.
Sorry to take this off topic.
--- rod.

David the H. · 01-11-2013, 09:26 AM

Code:

for dir in *; do \ls -1dQ $dir; done

Actually, the problem isn't the for loop. That's just fine:

globbing patterns expand last in the parsing order, after word-splitting is finished, so using them in for loops is no problem. In fact, it's recommended!

How can I find and deal with file names containing newlines, spaces or both?

The trouble here comes later on, when you try to expand the $dir variable. Now the unquoted variable gets split into individual "words", and ls gets handed a series of non-file names to try to parse.

The secret is to always ensure that your variables are double-quoted.

Code:

$ mkdir theNbomr; cd theNbomr; mkdir "Please explain"; mkdir "the downside of for loops"; mkdir "in this"; mkdir context.

$ for dir in *; do \ls -1dQ "$dir"; done
"context."
"in this"
"Please explain"
"the downside of for loops"

There are only a very few times when you'll ever want to leave quotes off, and that's only when you need the values to be word-split (and even then there are usually better techniques available). Beware also what I said about globbing too. If any of the filenames should happen to form valid globbing patterns themselves, they will also expand.

http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes

The danger of for loops is in trying to use them to process the contents of files or command output. Then it becomes very hard to properly word-split the content so that it can be safely parsed one line or section at a time. That's when the while+read loop should be used.

Don't Read Lines With For
How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?

A large number of scripting problems come down to not clearly understanding the command parsing order, what gets done before or after what. Learn that, and half of your troubles will go away.

http://mywiki.wooledge.org/BashParser
http://wiki.bash-hackers.org/syntax/grammar/parser_exec