Ubuntu – How to we remove text from start to some particular selected word using sed command in linux

bashcommand linesed

I have a simple query related to selection and replacing text in linux. I am using sed command. I have the following text:

hello world, I am just simple text for display.

Now I want to print to "hello world" only I can do it using following command in linux.

echo "hello world, I am just simple text for display." | sed 's/, I am.*//g'

Now I want totally inverse of this function, how can I remove "hello world" by using a simple command just like sed.

Output required:

, I am just simple text for display.

I would prefer if linux commands (sed etc) are used.

Best Answer

To reverse the effect of your command AND keeping the same part of the string to be matched (assuming that this is the only fix part of the string and you want to get rid of any other part that may vary), you can do :

echo "hello world, I am just simple text for display." | sed 's/^.*\(, I am.*\)/\1/g'

Result :

, I am just simple text for display

What the regular expression is doing :

^.* : matching any character at the beginning of the string until the next expression
$ & $ : to catch the part of the string which is matched by the expression in between (must be escaped by \ or they will match the parenthesis character).
, I am.* : the match you give us,
\1 : will be replaced by the result of the match of the first sub-expression between parenthesis

This way, you have the exact reverse effect of the command in your question, using the same part of the string to do the match.

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Ubuntu – Use of default alias “alert”

You could use the man pages to get details about what the commands combined here do. Here's a little about the purpose of those commands here:

"$([ $? = 0 ] && echo terminal || echo error)"

This would echo terminal or error as per to the execution status - successful or fail respectively of the last command; and the result is as the value to the -i switch of notify-send for displaying the icons.

history|tail -n1

..to get the last command executed.

and sed to parse the text to display it with notify-send message.

To understand these try the following:

true; echo "$([ $? = 0 ] && echo terminal || echo error)"

..this would echo terminal.

false; echo "$([ $? = 0 ] && echo terminal || echo error)"

..this would echo error.

notify-send -i terminal 'Please note the icon..' 'the default icon for the terminal has been used. You can specify any other icon of your choice'

And,

echo $?

..is very useful to know the exit value of the last command executed.

echo "$(echo "the output of this command enclosed within \$(...)") is being supplied here in the outer echo command where is used as an argument."

..nested echo as a simple demo for using $() in a command combo.

Ubuntu – Using sed to add text to a file before and after word

You can also process your list of words with the following perl command:

$ perl -ne 's/\s*$//; print "egrep -wi \047\|${_}\.\.nn\047 stats_all.txt > ${_}_frekvens.txt\n"' word_file.txt

Note that I'm using \047 to avoid escaping ' (single quote).

With a dummy word_file.txt:

foo
bar

The output is:

egrep -wi '\|foo\.\.nn' stats_all.txt > foo_frekvens.txt
egrep -wi '\|bar\.\.nn' stats_all.txt > bar_frekvens.txt

Best Answer

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Ubuntu – Use of default alias “alert”

Ubuntu – Using sed to add text to a file before and after word

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