Replace string in a file using bash

Question

I am trying to use the sed functionality of bash scripting to find and replce the content in a file. Not sure if my approach is correct or not but I dont want to go with regex.

Input:

 <if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>

    <VMArg name="-Dfile.encoding=UTF-8"/>
    <VMArg name="-Djava.util.logging.config.file=$VDISTDIR/system/conf/logging.properties"/>
    <VMArg name="-Dlog4j.configurationFile=file:///$VDISTDIR/system/conf/log4j2.yaml"/>

Expected:

 <if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>
This is the replaced text
    <VMArg name="-Dfile.encoding=UTF-8"/>
    <VMArg name="-Djava.util.logging.config.file=$VDISTDIR/system/conf/logging.properties"/>
    <VMArg name="-Dlog4j.configurationFile=file:///$VDISTDIR/system/conf/log4j2.yaml"/>

Trying to develop something like below but unfortunately its not working.

#!/bin/bash
find='<if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>

    <VMArg name="-Dfile.encoding=UTF-8"/>'

replace='<if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>

    <VMArg name="-Dfile.encoding=UTF-8"/>'

sed "s/$find/$replace/g" filename.input

Error:

sed: -e expression #1, char 7: unterminated `s' command

Please edit your question and explain what exactly means "unfortunately its not working". Why is there a \ before #!/bin/bash? — Bodo
– Bodo, Commented Oct 27, 2022 at 14:00
If the question is "replace empty row with text" this might work awk 'NF==0{$0 = "This is the replaced text"}1' file — Andre Wildberg
– Andre Wildberg, Commented Oct 27, 2022 at 14:01

Marek Knappe · Accepted Answer · 2022-10-27 14:07:06Z

2

The answer is: sed -i -e '1h;2,$H;$!d;g' -Ee 's/(<VMArg name="-Djava.awt.headless=true"\/>\n\s+<\/if>)/\1\nThis Is replaced text/' file

Working solution:

$ cat file
<if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>

    <VMArg name="-Dfile.encoding=UTF-8"/>
    <VMArg name="-Djava.util.logging.config.file=$VDISTDIR/system/conf/logging.properties"/>
    <VMArg name="-Dlog4j.configurationFile=file:///$VDISTDIR/system/conf/log4j2.yaml"/>

$ cat file  | sed -e '1h;2,$H;$!d;g' -Ee 's/(<VMArg name="-Djava.awt.headless=true"\/>\n\s+<\/if>)/\1\nThis Is replaced text/'
<if property="headless">
        <VMArg name="-Djava.awt.headless=true"/>
    </if>
This Is replaced text

    <VMArg name="-Dfile.encoding=UTF-8"/>
    <VMArg name="-Djava.util.logging.config.file=$VDISTDIR/system/conf/logging.properties"/>
    <VMArg name="-Dlog4j.configurationFile=file:///$VDISTDIR/system/conf/log4j2.yaml"/>```

answered Oct 27, 2022 at 14:07

Marek Knappe

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3 Comments

Jetchisel Over a year ago

No need for the cat though, just sed -e ... file

Marek Knappe Over a year ago

@Jetchisel In solution, there is sed without cat, you need -i to do in place change thought. The cat is only to show solution working :)

Jetchisel Over a year ago

Oh, right, I did not see that :-)

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