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转自
http://blog.jobbole.com/73257/
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“”（译注：指架构不清晰的软件系统）。
| 1 2 3 | readonly PROGNAME=$( basename $0) readonly PROGDIR=$(readlink -m $( dirname $0)) readonly ARGS= "$@" |
所有变量都应为局部的。
| 1 2 3 4 5 6 7 | change_owner_of_file() { local filename=$1 local user=$2 local group=$3 chown $user:$group $filename } |
| 1 2 3 4 5 6 7 8 9 10 11 | change_owner_of_files() { local user=$1; shift local group=$1; shift local files=$@ local i for i in $files do chown $user:$group $i done } |
| 1 2 | kfir@goofy ~ $ local a bash : local : can only be used in a function |
| 1 2 3 4 5 6 7 8 9 10 | main() { local files= "/tmp/a /tmp/b" local i for i in $files do change_owner_of_file kfir users $i done } main |
- 不可变的全局变量声明
- main()函数
| 1 2 3 | main() { local files=$( ls /tmp | grep pid | grep - v daemon) } |
| 1 2 3 4 5 6 7 8 9 10 11 | temporary_files() { local dir =$1 ls $ dir \ | grep pid \ | grep - v daemon } main() { local files=$(temporary_files /tmp ) } |
| 1 2 3 4 5 6 7 8 9 10 11 12 | test_temporary_files() { local dir = /tmp touch $ dir /a-pid1232 .tmp touch $ dir /a-pid1232-daemon .tmp returns "$dir/a-pid1232.tmp" temporary_files $ dir touch $ dir /b-pid1534 .tmp returns "$dir/a-pid1232.tmp $dir/b-pid1534.tmp" temporary_files $ dir } |
| 1 | bash -x my_prog.sh |
| 1 2 3 4 5 6 7 8 9 | temporary_files() { local dir =$1 set -x ls $ dir \ | grep pid \ | grep - v daemon set +x } |
| 1 2 3 4 5 6 7 8 | temporary_files() { echo $FUNCNAME $@ local dir =$1 ls $ dir \ | grep pid \ | grep - v daemon } |
调用函数：
| 1 | temporary_files /tmp |
会打印到标准输出：
| 1 | temporary_files /tmp |
这段代码做了什么？
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | main() { local dir = /tmp [[ -z $ dir ]] \ && do_something... [[ -n $ dir ]] \ && do_something... [[ -f $ dir ]] \ && do_something... [[ -d $ dir ]] \ && do_something... } main |
让你的代码说话：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | is_empty() { local var=$1 [[ -z $var ]] } is_not_empty() { local var=$1 [[ -n $var ]] } is_file() { local file =$1 [[ -f $ file ]] } is_dir() { local dir =$1 [[ -d $ dir ]] } main() { local dir = /tmp is_empty $ dir \ && do_something... is_not_empty $ dir \ && do_something... is_file $ dir \ && do_something... is_dir $ dir \ && do_something... } main |
| 1 2 3 4 5 | temporary_files() { local dir =$1 ls $ dir | grep pid | grep - v daemon } |
可以写得简洁得多：
| 1 2 3 4 5 6 7 | temporary_files() { local dir =$1 ls $ dir \ | grep pid \ | grep - v daemon } |
符号在行末的坏例子：（译注：原文在此例中用了temporary_files()代码段，疑似是贴错了。结合上下文，应为print_dir_if_not_empty()）
| 1 2 3 4 5 6 7 | print_dir_if_not_empty() { local dir =$1 is_empty $ dir && \ echo "dir is empty" || \ echo "dir=$dir" } |
好的例子：我们可以清晰看到行和连接符号之间的联系。
| 1 2 3 4 5 6 7 | print_dir_if_not_empty() { local dir =$1 is_empty $ dir \ && echo "dir is empty" \ || echo "dir=$dir" } |
不要这样做：
| 1 2 3 | echo "this prog does:..." echo "flags:" echo "-h print help" |
它应该是个函数：
| 1 2 3 4 5 | usage() { echo "this prog does:..." echo "flags:" echo "-h print help" } |
echo在每一行重复。因此我们得到了这个文档：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | usage() { cat <<- EOF usage: $PROGNAME options Program deletes files from filesystems to release space. It gets config file that define fileystem paths to work on, and whitelist rules to keep certain files. OPTIONS: -c --config configuration file containing the rules. use --help-config to see the syntax. -n --pretend do not really delete, just how what you are going to do . -t -- test run unit test to check the program - v --verbose Verbose. You can specify more then one - v to have more verbose -x --debug debug -h --help show this help --help-config configuration help Examples: Run all tests: $PROGNAME -- test all Run specific test : $PROGNAME -- test test_string.sh Run: $PROGNAME --config /path/to/config/ $PROGNAME.conf Just show what you are going to do : $PROGNAME -vn -c /path/to/config/ $PROGNAME.conf EOF } |
注意在每一行的行首应该有一个真正的制表符‘\t’。
在vim里，如果你的tab是4个空格，你可以用这个替换命令：
| 1 | :s/^ /\t/ |
这里是一个例子，完成了上面usage函数的用法。我从得到这段代码
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | cmdline() { # got this idea from here: # http://kirk.webfinish.com/2009/10/bash-shell-script-to-use-getopts-with-gnu-style-long-positional-parameters/ local arg= for arg do local delim= "" case "$arg" in #translate --gnu-long-options to -g (short options) --config) args= "${args}-c " ;; --pretend) args= "${args}-n " ;; -- test ) args= "${args}-t " ;; --help-config) usage_config && exit 0;; --help) args= "${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 ]] \ && 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：
| 1 2 3 4 | main() { cmdline $ARGS } main |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | test_config_line_paths() { local s= 'partition cpm-all, 80-90,' returns "/a" "config_line_paths '$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：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | DF= df mock_df_with_eols() { cat <<- 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 } |
这里我有个例外，为了测试，我在全局域中声明了DF为非只读。这是因为shunit2不允许改变全局域函数。
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