Find unique string within a file, up a line and append?

问题

Can someone please help me with this scenario? I'm looking for a SED or AWK command that I can use to find a unique string within a config file (Linux), go up a line and append a string to the end of that line?

For example:

config file:

define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com,
#MyUniqueString
}

In the above example, I'd like to use SED or AWK to find #MyUniqeString, go up a line that starts with members and append "domain4.com" at the end of the line.

I found this question below but I need to search the text file first for the string, and go one line above.

Bash script: Appending text at the last character of specific line of a file

Any suggestions?

回答1:

try this one-liner:

awk '{a[NR]=$0}/#MyUniqueString/{a[NR-1]=a[NR-1]"domain4.com"}END{for(i=1;i<=NR;i++)print a[i]}' configFile

test

kent$  cat test.txt 
define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com,
#MyUniqueString
}

kent$  awk '{a[NR]=$0}/#MyUniqueString/{a[NR-1]=a[NR-1]"domain4.com"}END{for(i=1;i<=NR;i++)print a[i]}' test.txt 
define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com,domain4.com
#MyUniqueString
}

回答2:

You can do this effectively with ed:

ed yourfile <<-'EOF'
    /#MyUniqueString/ # Find the matching line
    - # Go up a line
    a # Append text
    domain4.com
    . # Stop appending
    .-1,.j # Join the line above with the appended line
    w # Write the line
EOF

回答3:

here's another sed solution using backreferences:

sed '{N; N; s/\(.*\)\n\(#MyUniqueString\)/\1domain4.com\n\2/g}' config.file

回答4:

Comparission of three different solutions

Smaller, using `sed`:

sed -e ':a;N;/\n#MyUniqueString/{s/\n/ domain4.com\n/};H;s/\n.*$//;p;g;s/^.*\n//;ta;' config.file

This could be run as:

sed -e '
   :a;
    N;
    /\n#MyUniqueString/{
        s/\n/ domain4.com\n/
    };
    H;
    s/\n.*$//;
    p;
    g;
    s/^.*\n//;
    ta;
   ' config.file

profiling:

time sed ':a;N;/\n#MyUniqueString/{s/\n/ domain4.com\n/};H;
                      s/\n.*$//;p;g;s/^.*\n//;ta;' config.file 
define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com, domain4.com
#MyUniqueString
}



real    0m0.010s
user    0m0.000s
sys     0m0.008s

Why not pure bash ?

As there is no fork, this could be very quick (if from bash and for not too long config files):

readarray configFile < ./config.file
for ((i=${#configFile};i--;));do
    [[ "${configFile[i]}" =~ "#MyUniqueString" ]] && break
  done
configFile[i-1]+=" domain4.com"
printf "%s\n" "${configFile[@]//$'\n'/}"

profiling run by:

time {
    readarray configFile < ./config.file
    for ((i=${#configFile};i--;));do
        [[ "${configFile[i]}" =~ "#MyUniqueString" ]] && break
      done
    configFile[i-1]+=" domain4.com"
    printf "%s\n" "${configFile[@]//$'\n'/}"
}

Will give:

define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com, domain4.com
#MyUniqueString
}

real    0m0.001s
user    0m0.000s
sys     0m0.000s

Test with `awk`

time awk '{a[NR]=$0}/#MyUniqueString/{a[NR-1]=a[NR-1]" domain4.com"}END{for(i=1;i<=NR;i++)print a[i]}' config.file 
define hostgroup{
hostgroup_name http-urls ; The name of the hostgroup
alias HTTP URLs ; Long name of the group
members domain1.com, domain2.com, domain3.com, domain4.com
#MyUniqueString
}

real    0m0.009s
user    0m0.004s
sys     0m0.000s

回答5:

This awk solution only requires the previous line is remembered

awk '
    /#MyUniqueString/ {prev = prev "domain4.com"} 
    NR > 1 {print prev}
    {prev=$0}
    END {print prev}
'

来源：https://stackoverflow.com/questions/13958903/find-unique-string-within-a-file-up-a-line-and-append

标签

Linux

bash

sed

awk