一个修改配置文件的linux shell script

不久以前，曾经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，用到现在，感觉十分方便，感谢作者。

现在，需要通过web界面给用户留出接口来修改类似配置文件，大的方法是从php调用linux shell script，于是，现在贴一个可以修改此种配置文件的linux shell。

首先，配置文件的格式如下：

[unit1]
field1=value1
field2=value2

[unit2]
field1=value3
field3=value4

...
...

例子如下，config.ini：

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

[BUSINESS]
port=9084

[OFFLINE]
pcap_file=test.pcap

配置文件中包含3个unit，表示3个大的方面：数据库，业务，离线；每个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样的配置文件，而目前我们便是要通过linux shell来修改这个配置文件。

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 这样的格式（参数可以继续添加）来进行修改。

要做到修改配置文件的功能其实并不难，20-30行便可以解决问题。但是基于“一切输入都是有害的”的原则，需要在shell中加入各种容错处理，如果用户参数输入错误，要能及时提醒用户，定位问题所在，下面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

用户通过以下命令修改配置：

./modify_config_file BUSINESS-port=8888

输出如下：

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

其中，第一行表示找到BUSINESS这个unit所在的行号区间，注意是开区间；第二行表示所有匹配到field行号，因为可能多个unit中有相同的field；第三行表示最终落入unit区间的field行号；第四行表示所在行修改后的结果。

另外，用户输入不符合格式是很有可能，针对以下几种错误都会报告并且定位：

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

如果要应用到其它的配置文件，需要在脚本中修改配置文件所在路径与文件名：

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