问题描述
我正在从 OpenFoam 读取 shell 脚本 ( /opt/openfoam8/bin/foamCleanPath
)。在这个脚本中,有一个代码段:
for dir
do
....
done
我在下面的截图中标记了代码段。
但是我想知道为什么它不像for dir in someList
,并且在上面的代码段中没有dir
的定义。我该如何理解?
这是源代码:
#!/bin/sh
#------------------------------------------------------------------------------
# ========= |
# \\ / F ield | OpenFOAM: The Open Source CFD ToolBox
# \\ / O peration | Website: https://openfoam.org
# \\ / A nd | copyright (C) 2011-2018 OpenFOAM Foundation
# \\/ M anipulation |
#------------------------------------------------------------------------------
# License
# This file is part of OpenFOAM.
#
# OpenFOAM is free software: you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation,either version 3 of the License,or
# (at your option) any later version.
#
# OpenFOAM is distributed in the hope that it will be useful,but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# fitness FOR A PARTIculaR PURPOSE. See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License
# along with OpenFOAM. If not,see <http://www.gnu.org/licenses/>.
#
# Script
# foamCleanPath
#
# Description
# Usage: foamCleanPath [-strip] path [wildcard] .. [wildcard]
#
# Prints its argument (which should be a ':' separated path)
# without all
# - duplicate elements
# - elements whose start matches a wildcard
# - inaccessible directories (with the -strip (at your option)
#
# Note
# - this routine will fail when directories have embedded spaces
# - false matches possible if a wildcard contains '.' (sed regex)
# - the wildcards can themselves can be written together and separated
# by colons or whitespace
#------------------------------------------------------------------------------
usage() {
cat <<USAGE
Usage: ${0##*/} [OPTION] path [wildcard1] .. [wildcardN]
options:
-strip remove inaccessible directories
-help print the usage
Prints its argument (which should be a ':' separated list) cleansed from
- duplicate elements
- elements whose start matches one of the wildcard(s)
- inaccessible directories (with the -strip option)
Exit status
0 on success
1 for miscellaneous errors.
2 initial value of 'path' is empty
USAGE
}
error() {
usage 1>&2
exit 1
}
unset strip
# parse options
while [ "$#" -gt 0 ]
do
case "$1" in
-h | -help)
usage && exit 0
;;
-strip)
strip=true
shift
;;
-*)
error
;;
*)
break
;;
esac
done
[ "$#" -ge 1 ] || error
dirList="$1"
shift
[ -n "$dirList" ] || exit 2 # quick exit on empty 'dirList'
##DEBUG echo "input>$dirList<" 1>&2
# preserve current IFS and split on colon or whitespace
oldIFS="$IFS"
IFS=': '
# "wildcard1 ... wildcardN" may have been passed as a single parameter
# or may contain ':' separators
set -- $*
# strip out wildcards via sed
while [ "$#" -ge 1 ]
do
wildcard=$1
shift
##DEBUG echo "remove>$wildcard<" 1>&2
if [ -n "$wildcard" ]
then
dirList=$(echo "$dirList:" | sed -e "s|${wildcard}[^:]*:||g")
fi
done
# split on ':' (and on space as well to avoid any surprises)
IFS=': '
set -- $dirList
##DEBUG echo "intermediate>$dirList<" 1>&2
# rebuild the list from scratch
unset dirList
for dir
do
##DEBUG echo "check>$dir<" 1>&2
#- dirs must exist
if [ -e "$dir" ]
then
#- no duplicate dirs
duplicate=$(echo " $dirList " | sed -ne "s: $dir :DUP:p")
if [ ! "$duplicate" ]
then
dirList="$dirList $dir"
fi
elif [ "$strip" != true ]
then
# Print non-existing directories if not in 'strip' mode.
dirList="$dirList $dir"
fi
done
# split on whitespace
IFS=' '
set -- $dirList
# rejoin on ':'
IFS=':'
dirList="$*"
# restore IFS
IFS="$oldIFS"
##DEBUG echo "output>$dirList<" 1>&2
echo "$dirList"
#------------------------------------------------------------------------------
解决方法
引用 Bash man page,这是实现 /bin/sh
的一种更常见的 shell:
for name [ [ in [ word ... ] ] ; ] do list ; done
in
后面的单词列表被扩展,生成一个项目列表。变量name依次设置给这个列表的每个元素,每次都执行list。如果 in
word 被省略,for
命令会为设置的每个位置参数执行一次 list [...]
因此,如果省略 in ...
部分,循环将迭代当前上下文中设置的位置参数($1
、$2
、...)。在您的情况下,这将是作为命令行参数给出的 通配符 列表。