BASH的保护性编程技巧

2014-7-18 14:26| 发布者: joejoe0332| 查看: 3788| 评论: 0|原作者: cjpan|来自: 伯乐在线

摘要: 这是我写BASH程序的招式。这里本没有什么新的内容，但是从我的经验来看，人们爱滥用BASH。他们忽略了计算机科学，而从他们的程序中创造的是“大泥球”（译注：指架构不清晰的软件系统）。 ...

命令行参数

这里是一个例子，完成了上面usage函数的用法。我从Kirk’s blog post – bash shell script to use getopts with gnu style long positional parameters得到这段代码

cmdline() {
    # got this idea from here:
    # http://kirk.webfinish.com/2009/10/bash-shell-script-to-use-getopts-with-gnu-style-long-positional-parameters/
    local arg=
    for arg
    do
        local delim=""
        case "$arg" in
            #translate --gnu-long-options to -g (short options)
            --config)         args="${args}-c ";;
            --pretend)        args="${args}-n ";;
            --test)           args="${args}-t ";;
            --help-config)    usage_config &amp;&amp; exit 0;;
            --help)           args="${args}-h ";;
            --verbose)        args="${args}-v ";;
            --debug)          args="${args}-x ";;
            #pass through anything else
            *) [[ "${arg:0:1}" == "-" ]] || delim="\""
                args="${args}${delim}${arg}${delim} ";;
        esac
    done
 
    #Reset the positional parameters to the short options
    eval set -- $args
 
    while getopts "nvhxt:c:" OPTION
    do
         case $OPTION in
         v)
             readonly VERBOSE=1
             ;;
         h)
             usage
             exit 0
             ;;
         x)
             readonly DEBUG='-x'
             set -x
             ;;
         t)
             RUN_TESTS=$OPTARG
             verbose VINFO "Running tests"
             ;;
         c)
             readonly CONFIG_FILE=$OPTARG
             ;;
         n)
             readonly PRETEND=1
             ;;
        esac
    done
 
    if [[ $recursive_testing || -z $RUN_TESTS ]]; then
        [[ ! -f $CONFIG_FILE ]] \
            &amp;&amp; eexit "You must provide --config file"
    fi
    return 0
}

你像这样，使用我们在头上定义的不可变的ARGS变量：

main() {
    cmdline $ARGS
}
main

单元测试

在更高级的语言中很重要。
使用shunit2做单元测试

test_config_line_paths() {
    local s='partition cpm-all, 80-90,'
 
    returns "/a" "config_line_paths '$s /a, '"
    returns "/a /b/c" "config_line_paths '$s /a:/b/c, '"
    returns "/a /b /c" "config_line_paths '$s   /a  :    /b : /c, '"
}
 
config_line_paths() {
    local partition_line="$@"
 
    echo $partition_line \
        | csv_column 3 \
        | delete_spaces \
        | column 1 \
        | colons_to_spaces
}
 
source /usr/bin/shunit2

这里是另一个使用df命令的例子：

DF=df
 
mock_df_with_eols() {
    cat &lt;&lt;- EOF
    Filesystem           1K-blocks      Used Available Use% Mounted on
    /very/long/device/path
                         124628916  23063572 100299192  19% /
    EOF
}
 
test_disk_size() {
    returns 1000 "disk_size /dev/sda1"
 
    DF=mock_df_with_eols
    returns 124628916 "disk_size /very/long/device/path"
}
 
df_column() {
    local disk_device=$1
    local column=$2
 
    $DF $disk_device \
        | grep -v 'Use%' \
        | tr '\n' ' ' \
        | awk "{print \$$column}"
}
 
disk_size() {
    local disk_device=$1
 
    df_column $disk_device 2
}