如何在 shell 脚本中使用 for 循环

Question

这是shell脚本代码

if [ -z "$1" ]
then
echo "src directory will be considered for analysis"  
${PYTHON3_ENV} $sca_wrapper_path/astree_launcher/create_astree_config.py ${prjRoot} ${OUTDIR} ${prjRoot}/src
else
echo "Dax file will be created for the selected folders"
${PYTHON3_ENV} -m pip install -r ${SCA_WRAPPER_PATH}/requirements.txt
set +u
# optional argument. In case arguments are not provided, empty string will be set intentionally
export SCA_include1=$2
export SCA_include2=$3
export SCA_include3=$4
export SCA_include4=$5
export SCA_include5=$6
export SCA_include6=$7
export SCA_include7=$8
export SCA_include8=$9
set -u
${PYTHON3_ENV} $sca_wrapper_path/astree_launcher/create_astree_config.py ${OPTION1} ${prjRoot} ${OUTDIR} ${SCA_include1} ${SCA_include2} ${SCA_include3} ${SCA_include4} ${SCA_include5} ${SCA_include6} ${SCA_include7} ${SCA_include8}
fi

在这个 Bash 脚本中，我可以使用 for 循环

export SCA_include1=$2
export SCA_include2=$3
export SCA_include3=$4
export SCA_include4=$5
export SCA_include5=$6
export SCA_include6=$7
export SCA_include7=$8
export SCA_include8=$9

并减少行数，请帮助我

Answer 1

通常，您可以通过"$@"访问所有位置参数，这将扩展到每个位置参数(如果没有，则扩展到空字符串)。 您的代码段可以重写：

if [ -n "$1" ]; then
echo "Dax file will be created for the selected folders"
${PYTHON3_ENV} -m pip install -r ${SCA_WRAPPER_PATH}/requirements.txt
option1=$1  # This is my guess as to what OPTION1 is
shift       # remove $1 so that "$@" does not repeat it
if test $# -lt 8; then
echo 'You must pass at least 8 arguments' >&2
exit 1
fi
else
echo "src directory will be considered for analysis"
unset option1
unset outdir
set -- "${prjRoot}/src"  # Append $prjRoot/src so that "$@" expands to "${prjRoot}/src"
fi
# See discussion below on quoting
${PYTHON3_ENV} $sca_wrapper_path/astree_launcher/create_astree_config.py 
${option1:+"$option1"} "${prjRoot}" ${outdir:+"$outdir"} "$@"

请注意，原始代码使用set -u来确保设置特定数量的位置参数。 这种类型的检查可以通过评估$#来完成。

另请注意，引用在这里真的很重要。 通常，最佳做法是双引号变量，上面的命令几乎肯定应该在${prjRoot}周围加上引号，但你不能简单地引用${option1}或${outdir}，因为你希望它们扩展到零。 将空字符串作为参数传递与根本不传递参数非常不同，如果您引用这些变量，您将获得前一种行为。 上面使用${option1:+"$option1"}，它扩展到空字符串(因此根本不传递任何参数)，或者引用$option1的值(因此禁止字段拆分并且只传递一个参数)。 我怀疑outdir和option1可以更干净地处理，但您尚未显示完整的代码，因此很难确定。 我不清楚如果${prjRoot}为空，您应该如何处理它，所以我假设案例在脚本的前面处理(例如，通过中止并显示错误消息)。

Answer 2

尝试：

for i in {2..9}; do
export "SCA_include$((i-1))=${!i}"
done

• ${!i}是可变的间接。 请参阅 Bash 参考手册中的外壳参数扩展。