Add bash pitfalls module

modules/bashpf.pl

@@ -0,0 +1,45 @@
+#!/usr/bin/perl -w
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+my $query = "@ARGV";
+print "Usage: pf <id or search text>\n" and exit 0 if not length $query;
+
+my (%pf, $match);
+
+open(FILE, "< bashpf.txt") or print "Can't open Bash Pitfalls: $!" and exit 1;
+
+foreach my $line (<FILE>) {
+    if ($line =~ /^(\d+)\.\s+(.*)$/) {
+        $pf{$1} = $2;
+    }
+}
+
+close FILE;
+
+if ($query =~ / >/) {
+    $rcpt = $query;
+    $query =~ s/ +>.*$//;
+    $rcpt =~ s/^.* > *//;
+}
+
+if (exists $pf{$query}) {
+    $match = $query;
+} else {
+    foreach my $key (keys %pf) {
+        if ($pf{$key} =~ /$query/i) {
+            $match = $key;
+            last;
+        }
+    }
+}
+
+if ($match) {
+    my $id = "pf$match";
+    print "$rcpt: " if $rcpt;
+    print "https://mywiki.wooledge.org/BashPitfalls#$id -- Don't do this! -- $pf{$match}\n";
+} else {
+    print "No matches found at https://mywiki.wooledge.org/BashPitfalls\n";
+}

modules/bashpf.txt

@@ -0,0 +1,62 @@
+1.     for f in $(ls *.mp3)
+2.     cp $file $target
+3.     Filenames with leading dashes
+4.     [ $foo = "bar" ]
+5.     cd $(dirname "$f")
+6.     [ "$foo" = bar && "$bar" = foo ]
+7.     [[ $foo > 7 ]]
+8.     grep foo bar | while read -r; do ((count++)); done
+9.     if [grep foo myfile]
+10.     if [bar="$foo"]; then ...
+11.     if [ [ a = b ] && [ c = d ] ]; then ...
+12.     read $foo
+13.     cat file | sed s/foo/bar/ > file
+14.     echo $foo
+15.     $foo=bar
+16.     foo = bar
+17.     echo <<EOF
+18.     su -c 'some command'
+19.     cd /foo; bar
+20.     [ bar == "$foo" ]
+21.     for i in {1..10}; do ./something &; done
+22.     cmd1 && cmd2 || cmd3
+23.     echo "Hello World!"
+24.     for arg in $*
+25.     function foo()
+26.     echo "~"
+27.     local var=$(cmd)
+28.     export foo=~/bar
+29.     sed 's/$foo/good bye/'
+30.     tr [A-Z] [a-z]
+31.     ps ax | grep gedit
+32.     printf "$foo"
+33.     for i in {1..$n}
+34.     if [[ $foo = $bar ]] (depending on intent)
+35.     if [[ $foo =~ 'some RE' ]]
+36.     [ -n $foo ] or [ -z $foo ]
+37.     [[ -e "$broken_symlink" ]] returns 1 even though $broken_symlink exists
+38.     ed file <<<"g/d\{0,3\}/s//e/g" fails
+39.     expr sub-string fails for "match"
+40.     On UTF-8 and Byte-Order Marks (BOM)
+41.     content=$(<file)
+42.     for file in ./* ; do if [[ $file != *.* ]]
+43.     somecmd 2>&1 >>logfile
+44.     cmd; (( ! $? )) || die
+45.     y=$(( array[$x] ))
+46.     read num; echo $((num+1))
+47.     IFS=, read -ra fields <<< "$csv_line"
+48.     export CDPATH=.:~/myProject
+49.     OIFS="$IFS"; ...; IFS="$OIFS"
+50.     hosts=( $(aws ...) )
+51.     Non-atomic writes with xargs -P
+52.     find . -exec sh -c 'echo {}' \;
+53.     sudo mycmd > /myfile
+54.     sudo ls /foo/*
+55.     myprogram 2>&-
+56.     Using xargs without -0
+57.     unset a[0]
+58.     month=$(date +%m); day=$(date +%d)
+59.     i=$(( 10#$i ))
+60.     set -euo pipefail
+61.     [[ -v hash[$key] ]]
+62.     (( hash[$key]++ ))