用awk替换文件中的字符串（如sed -i一样）

Question

I have an Openwrt wireless config file. Format is like this:

config wifi-iface 'priv'
    option device 'radio0'
    option ifname 'priv0'
    option mode 'ap'
    option encryption 'psk-mixed'
    option macfilter 'allow'
    option macfile '/tmp/mac_filter_priv'
    option disabled '1'
    option hidden '1

config wifi-iface 'orphan'
    option device 'radio0'

What I need to do is find exactly wifi-iface 'priv' and change option disabled from 1 to 0. I tried to do it with awk like this:

awk 'BEGIN{f=0} /wifi-iface \47priv/{f=1} {if(f==1 && $2=="disabled")
 {gsub("1", "0"); f=0; print}}' wireless

Seems fine but I can't do it interactively so file not changed. How to do that if awk doesn't support -i option?

Answer 1

You can use this awk command with null RS (record separator):

awk -v RS= '/wifi-iface \047priv/{sub(/option disabled [^\n]*/, 
       "option disabled \047" 0 "\047"); print $0 ORS; next} 1' config
config wifi-iface 'priv'
    option device 'radio0'
    option ifname 'priv0'
    option mode 'ap'
    option encryption 'psk-mixed'
    option macfilter 'allow'
    option macfile '/tmp/mac_filter_priv'
    option disabled '0'
    option hidden '1
config wifi-iface 'orphan'
    option device 'radio0'

Answer 2

Must it be awk ? You could use sed , which does have a -i option:

sed -i "/^config wifi-iface 'priv'/,/^config /s/\( disabled\) '1'/\1 '0'/" wireless

Here, the leading address pair restricts the s command to the section with the iface 'priv'.

Answer 3

Using GNU awk for -i inplace (and tidying up the script):

$ cat tst.awk
/config wifi-iface / { f = (/\047priv\047/ ? 1 : 0) }
f && $2=="disabled" { sub(/1/,"0") }
{ print }

$ awk -i inplace -f tst.awk file

$ cat file
config wifi-iface 'priv'
    option device 'radio0'
    option ifname 'priv0'
    option mode 'ap'
    option encryption 'psk-mixed'
    option macfilter 'allow'
    option macfile '/tmp/mac_filter_priv'
    option disabled '0'
    option hidden '1

config wifi-iface 'orphan'
    option device 'radio0'

With any other awk you can always do (as with any UNIX command):

awk -f tst.awk file > tmp && mv tmp file

or if you are severely allergic to tmp files:

$ cat tst.awk
/config wifi-iface / { f = (/\047priv\047/ ? 1 : 0) }
f && $2=="disabled" { sub(/1/,"0") }
{ rec = rec $0 RS }
END { close(FILENAME); printf "%s", rec > FILENAME }

$ awk -f tst.awk file

$ cat file
config wifi-iface 'priv'
    option device 'radio0'
    option ifname 'priv0'
    option mode 'ap'
    option encryption 'psk-mixed'
    option macfilter 'allow'
    option macfile '/tmp/mac_filter_priv'
    option disabled '0'
    option hidden '1

config wifi-iface 'orphan'
    option device 'radio0'