一个改动配置文件的linux shell script

不久以前，以前搜到一篇博客是读取配置文件的，http://www.cnblogs.com/bo083/archive/2012/11/19/2777076.html，用到如今，感觉十分方便。感谢作者。

如今，须要通过web界面给用户留出接口来改动类似配置文件，大的方法是从php调用linux shell script，于是，如今贴一个能够改动此种配置文件的linux shell。

首先，配置文件的格式例如以下：

[unit1]
field1=value1
field2=value2

[unit2]
field1=value3
field3=value4

...
...

样例例如以下，config.ini：

[DATABASE]
dbms_ip=localhost
user=root
passwd=cloud
db_name=cloud
port=2394

[BUSINESS]
port=9084

[OFFLINE]
pcap_file=test.pcap

配置文件里包括3个unit。表示3个大的方面：数据库，业务，离线；每一个unit有属于自己的字段名及字段值。

上文中引用博客正是能读取这种配置文件。而眼下我们便是要通过linux shell来改动这个配置文件。

我们设计的程序名为 modify_config_file，使用 ./modify_config_file unit1-field1=changed_value1 unit2-field1=changed_value2 这种格式（參数能够继续加入）来进行改动。

要做到改动配置文件的功能事实上并不难，20-30行便能够解决这个问题。

可是基于“一切输入都是有害的”的原则，须要在shell中增加各种容错处理，假设用户參数输入错误，要能及时提醒用户。定位问题所在。以下是基于这样一个初衷的shell。当然，名称为modify_config_file：

#!/bin/bash
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
export PATH

#Program
#	This program is to modify the configuration file 
#History
#	2014.10.30   WeiZheng	  1.1

MY_HOME="/home/weizheng/10-30-yg/yg-soft"
CONFIG_FILE="$MY_HOME/config.ini"
ERROR_NUM=255

function get_line_num()
{
	# Check if the argument name has the separator "-" that separate the argument unit and argument field
	separator=$(echo $1 | grep "-")
	if [ -z "$separator" ]; then
		echo -e "error: \"$1\": argument name has no separator \"-\" that separate the argument unit and argument field"
		exit $ERROR_NUM
	fi

	# Check if the argument name has argument unit and argument field
	arg_unit=$(echo $1 | cut -d "-" -f 1)
	arg_field=$(echo $1 | cut -d "-" -f 2)
	if [ -z "$arg_unit" -o -z "$arg_field" ]; then
		echo -e "error: \"$1\": argument name has no argument unit or argument field around \"-\""
		exit $ERROR_NUM
	fi

	# Get the argument unit's interval [$arg_unit_line_num, $next_neighbour_unit_line_num)
	arg_unit_line_num=$(grep -n "\[$arg_unit\]" $CONFIG_FILE | cut -d ":" -f1)
	if [ -z "$arg_unit_line_num" ]; then
		echo -e "error: \"$arg_unit\": can not find argument unit"
		exit $ERROR_NUM
	fi

	next_neighbour_unit_line_num=$(awk "NR>$arg_unit_line_num && /^\[.*\]/ {print NR; exit 0}" $CONFIG_FILE)
	if [ -z "$next_neighbour_unit_line_num" ]; then
		file_line_count=$(wc -l $CONFIG_FILE | cut -d " " -f 1)
		next_neighbour_unit_line_num=$((file_line_count+1))
	fi
	echo "argument unit interval:          ($arg_unit_line_num, $next_neighbour_unit_line_num)"

	arg_field_line_nums=$(grep -n "^$arg_field=" $CONFIG_FILE | cut -d ":" -f1 | tr "\n" "\ ")
	if [ -z "$arg_field_line_nums" ]; then
		echo -e "error: \"$arg_field\": can not find argument field"
		exit $ERROR_NUM
	fi
	echo "matched argument field in line:  $arg_field_line_nums"

	# the $arg_field_line_num must in the interval ($arg_unit_line_num, $next_neighbour_unit_line_num)
	for arg_field_line_num in $arg_field_line_nums
	do
		if [ $arg_field_line_num -gt $arg_unit_line_num -a $arg_field_line_num -lt $next_neighbour_unit_line_num ]; then
			echo "find argument field in line:     $arg_field_line_num"
			return $arg_field_line_num
		fi
	done

	# if not return in for-loop, the arg_field_line_num is not in the interval ($arg_unit_line_num, $next_neighbour_unit_line_num)
	echo -e "the argument field is not in the argument unit interval"
	exit $ERROR_NUM
}

while [ "$1" ]
do
	# Check if the separator "=" that separate the argument name and argument value exists
	equal_symbol=$(echo $1 | grep "=")
	if [ -z "$equal_symbol" ]; then
		echo -e "error: \"$1\": argument has no \"=\""
		exit $ERROR_NUM
	fi

	# Check if argument name and argument value exist
	arg_name=$(echo $1 | cut -d "=" -f 1)
	arg_value=$(echo $1 | cut -d "=" -f 2)
	if [ -z "$arg_name" -o -z "$arg_value" ]; then
		echo -e "error: \"$1\": argument has no name or value around \"=\""
		exit $ERROR_NUM
	fi

	# Get the line number of the argument from CONFIG_FILE
	get_line_num $arg_name
	args_line_num=$?
	
	# use sed change the argument line
	arg_field=$(echo $arg_name | cut -d "-" -f 2)
	sed -i "${args_line_num}c $arg_field=$arg_value" $CONFIG_FILE
	new_line=$(sed -n "${args_line_num}p" $CONFIG_FILE)
	echo "the argument has been changed:   $new_line"
	shift 1
done

用户通过下面命令改动配置：

./modify_config_file BUSINESS-port=8888

输出例如以下：

argument unit interval:          (8, 11)
matched argument field in line:  6 9 
find argument field in line:     9
the argument has been changed:   port=8888

当中，第一行表示找到BUSINESS这个unit所在的行号区间，注意是开区间。第二行表示全部匹配到field行号。由于可能多个unit中有同样的field。第三行表示终于落入unit区间的field行号；第四行表示所在行改动后的结果。

另外，用户输入不符合格式是非常有可能。针对下面几种错误都会报告而且定位：

1. ./modify_config_file BUSINESS
error: "BUSINESS": argument has no "="
2. ./modify_config_file BUSINESS=
error: "BUSINESS=": argument has no name or value around "="
3. ./modify_config_file BUSINESS=8888
error: "BUSINESS": argument name has no separator "-" that separate the argument unit and argument field
4. ./modify_config_file BUSINESS-=8888
error: "BUSINESS-": argument name has no argument unit or argument field around "-"
5. ./modify_config_file BUSINESS-por=8888
argument unit interval:          (8, 11)
error: "por": can not find argument field
6. ./modify_config_file BUSINE-port=8888
error: "BUSINE": can not find argument unit

假设要应用到其他的配置文件，须要在脚本中改动配置文件所在路径与文件名称：

MY_HOME="/home/weizheng/10-30-yg/yg-soft"
CONFIG_FILE="$MY_HOME/config.ini"