Select random lines from a file
Use shuf with the -n option as shown below, to get N random lines: shuf -n N input > output
text-processing
Using multiple delimiters in awk
The delimiter can be a regular expression. awk -F'[/=]’ ‘{print $3 “\t” $5 “\t” $8}’ file Produces: tc0001 tomcat7.1 demo.example.com tc0001 tomcat7.2 quest.example.com tc0001 tomcat7.5 www.example.com
Using SQL to determine word count stats of a text field
The text handling capabilities of MySQL aren’t good enough for what you want. A stored function is an option, but will probably be slow. Your best bet to process the data within MySQL is to add a user defined function. If you’re going to build a newer version of MySQL anyway, you could also add … Read more
How to replace ${} placeholders in a text file?
Update Here is a solution from yottatsa on a similar question that only does replacement for variables like $VAR or ${VAR}, and is a brief one-liner i=32 word=foo envsubst < template.txt Of course if i and word are in your environment, then it is just envsubst < template.txt On my Mac it looks like it … Read more
How to add a new line of text to an existing file in Java? [duplicate]
you have to open the file in append mode, which can be achieved by using the FileWriter(String fileName, boolean append) constructor. output = new BufferedWriter(new FileWriter(my_file_name, true)); should do the trick
How to delete all blank lines in the file with the help of python?
The with statement is excellent for automatically opening and closing files. with open(‘myfile’,’rw’) as file: for line in file: if not line.isspace(): file.write(line)
Add a prefix string to beginning of each line
# If you want to edit the file in-place sed -i -e ‘s/^/prefix/’ file # If you want to create a new file sed -e ‘s/^/prefix/’ file > file.new If prefix contains /, you can use any other character not in prefix, or escape the /, so the sed command becomes ‘s#^#/opt/workdir#’ # or ‘s/^/\/opt\/workdir/’
How can I extract a predetermined range of lines from a text file on Unix?
sed -n ‘16224,16482p;16483q’ filename > newfile From the sed manual: p – Print out the pattern space (to the standard output). This command is usually only used in conjunction with the -n command-line option. n – If auto-print is not disabled, print the pattern space, then, regardless, replace the pattern space with the next line … Read more
How to use sed to replace only the first occurrence in a file?
A sed script that will only replace the first occurrence of “Apple” by “Banana” Example Input: Output: Apple Banana Apple Apple Orange Orange Apple Apple This is the simple script: Editor’s note: works with GNU sed only. sed ‘0,/Apple/{s/Apple/Banana/}’ input_filename The first two parameters 0 and /Apple/ are the range specifier. The s/Apple/Banana/ is what … Read more
How do you delete all lines that contain no letters from the alphabet using either grep, sed, or awk? [closed]
With GNU grep: grep ‘[[:alpha:]]’ file or GNU sed: sed ‘/[[:alpha:]]/!d’ file Output: 0hjjAby68xp H5e