Bash Text Processing – How to Append Text to Beginning and End of Multiple Text Files

filesshell-scripttext processing

I have a directory full of text files. My goal is to append text to the beginning and end of all of them. The text that goes at the beginning and end is the same for each file.

Based on code I got from the web, this is the code for appending to the beginning of the file:

echo -e 'var language = {\n$(cat $BASEDIR/Translations/Javascript/*.txt)' > $BASEDIR/Translations/Javascript/*.txt

This is the code for appending to the end of the file. The goal is to add the text }; at the end of each file:

echo "};" >> $BASEDIR/Translations/Javascript/*.txt

The examples I drew from were for acting on individual files. I thought I'd try acting on multiple files using the wildcard, *.txt.

I might be making other mistakes as well. In any case, how do I append text to the beginning and end of multiple files?

Best Answer

To prepend text to a file you can use (with the GNU implementation of sed):

sed -i '1i some string' file

Appending text is as simple as

echo 'Some other string' >> file

The last thing to do is to put that into a loop which iterates over all the files you intend to edit:

for file in *.txt; do
  sed -i '1i Some string' "$file" &&
  echo 'Some other string' >> "$file"
done

Related Solutions

Shell Script – Adding Lines to the Beginning and End of a Huge File

sed -i uses tempfiles as an implementation detail, which is what you are experiencing; however, prepending data to the beginning of a data stream without overwriting the existing contents requires rewriting the file, there's no way to get around that, even when avoiding sed -i.

If rewriting the file is not an option, you might consider manipulating it when it is read, for example:

{ echo some prepended text ; cat file ; } | command

Also, sed is for editing streams -- a file is not a stream. Use a program that is meant for this purpose, like ed or ex. The -i option to sed is not only not portable, it will also break any symlinks to your file, since it essentially deletes it and recreates it, which is pointless.

You can do this in a single command with ed like so:

ed -s file << 'EOF'
0a
prepend these lines
to the beginning
.
$a
append these lines
to the end
.
w
EOF

Note that depending on your implementation of ed, it may use a paging file, requiring you to have at least that much space available.

Best Answer

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Shell Script – Adding Lines to the Beginning and End of a Huge File

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