如何创建带有可选参数的bash脚本的一个标志

Question

我试图创建一个脚本这将有可选选项的标志。使用getopts可以在标志后面指定一个强制参数（使用冒号），但我想保留它为可选。

这将是这样的：

./install.sh -a 3 

或

./install.sh -a3 

其中 'a' 是标志和 '3' 是个遵循可选参数。

在此先感谢。

Answer 1

getopt exter nal程序允许选项通过向选项名称添加双冒号来获得单个可选参数。

# Based on a longer example in getopt-parse.bash, included with 
# getopt 
TEMP=$(getopt -o a:: -- "$@") 
eval set -- "$TEMP" 
while true ; do 
    case "$1" in 
    -a) 
     case "$2" in 
      "") echo "Option a, no argument"; shift 2 ;; 
      *) echo "Option a, argument $2"; shift 2;; 
     esac ;; 
    --) shift; break ;; 
    *) echo "Internal error!"; exit 1 ;; 
    esac 
done 

Answer 2

使用getopt的功能。在大多数系统中，man getopt将产生文档它，甚至在脚本中使用它的例子。从我系统上的手册页：

以下代码片段显示了如何处理参数 以获取可以采用选项-a和-b以及需要参数的选项-o， 的命令。

 args=`getopt abo: $*` 
     # you should not use `getopt abo: "$@"` since that would parse 
     # the arguments differently from what the set command below does. 
     if [ $? != 0 ] 
     then 
       echo 'Usage: ...' 
       exit 2 
     fi 
     set -- $args 
     # You cannot use the set command with a backquoted getopt directly, 
     # since the exit code from getopt would be shadowed by those of set, 
     # which is zero by definition. 
     for i 
     do 
       case "$i" 
       in 
         -a|-b) 
           echo flag $i set; sflags="${i#-}$sflags"; 
           shift;; 
         -o) 
           echo oarg is "'"$2"'"; oarg="$2"; shift; 
           shift;; 
         --) 
           shift; break;; 
       esac 
     done 
     echo single-char flags: "'"$sflags"'" 
     echo oarg is "'"$oarg"'" 

此代码将接受任何以下作为等效的：

 cmd -aoarg file file 
     cmd -a -o arg file file 
     cmd -oarg -a file file 
     cmd -a -oarg -- file file 

Answer 3

在bash有一些隐变量：

$#: contains number of arguments for a called script/function 

    $0: contains names of script/function 
    $1: contains first argument 
    $2: contains second argument 
    ... 
    $n: contains n-th argument 

例如：

#!/bin/ksh 

    if [ $# -ne 2 ] 
    then 
     echo "Wrong number of argument - expected 2 : $#" 
    else 
     echo "Argument list:" 
     echo "\t$0" 
     echo "\t$1" 
     echo "\t$2" 
    fi 

Answer 4

我的解决办法：

#!/bin/bash 
count=0 
skip=0 
flag="no flag" 
list=($@) #put args in array 
for arg in $@ ; do #iterate over array 
    count=$(($count+1)) #update counter 
    if [ $skip -eq 1 ]; then #check if we have to skip this args 
     skip=0 
     continue 
    fi 
    opt=${arg:0:2} #get only first 2 chars as option 
    if [ $opt == "-a" ]; then #check if option equals "-a" 
     if [ $opt == $arg ] ; then #check if this is only the option or has a flag 
      if [ ${list[$count]:0:1} != "-" ]; then #check if next arg is an option 
       skip=1 #skip next arg 
       flag=${list[$count]} #use next arg as flag 
      fi 
     else 
      flag=${arg:2} #use chars after "-a" as flag 
     fi 
    fi 
done 

echo $flag 

Answer 5

以下是没有getopt，它需要一个可选的参数与-a标志：

for WORD; do 
     case $WORD in 
      -a?) echo "single arg Option" 
       SEP=${WORD:2:1} 
       echo $SEP 
       shift ;; 
      -a) echo "split arg Option" 
       if [[ ${2:0:1} != "-" && ${2:0:1} != ""]] ; then 
       SEP=$2 
       shift 2 
       echo "arg present" 
       echo $SEP 
       else 
       echo "optional arg omitted" 
       fi ;; 
      -a*) echo "arg Option" 
       SEP=${WORD:2} 
       echo $SEP 
       shift ;; 
      -*) echo "Unrecognized Short Option" 
       echo "Unrecognized argument" 
      ;; 
     esac 
done 

其他选项/标志也可以很容易地添加。