less, more, head, tail, cat and nano

Reading and writing text files

Open and read files : less or more

Softwares to open text files as read-only.

• Use less --help or man less to see a manual on how to use less and more --help or man more to see how to use more
• less file1
  • Will open file1 to read. If you want to look for a word, type / then type the word.
• less file1 file2 file3
  • Will open the three files to read. You can move between the files by typing : followed by p to look at the previous file or n to look at the next one.

less can read fastq.gz files (compressed files)

Print text to the screen : cat

Prints file to the screen

• cat file1: will print the content of file1 to the screen. If the file is a binary file (.bam), or if it is compressed (.zip, .tar, .gz), the printed text will be all gibberish
• cat file1 file2: will print the content of file1 followed by the content of file 2
• cat file1 > file2; cat file3 >> file2: is the same as cat file1 file3 > file2.

In the case of compressed text files, like fastq.gz, we can read it with zcat

View beginning or end of a file : head and tail

Prints the first (head) or last (tail) 10 lines of a file to the screen. If you have a big file and you just want to see if it looks fine or what it contains, use this

• head file1: will print the first 10 lines of file1
• head -n 20 file1: the option -n allows you to specify the number of lines you want to be printed

The behavior of tail is similar to head.

Edit text file : nano

Software to edit text in the server. Used alone will open an empty file. When you try to close the file (Ctrl + x) will ask if you want to save it and ask for a name for the path where to save it.

• nano file1
  • Will open file1 for edition. If file1 does not exist, will create it.
• nano *
  • Will open all text files in the working directory for edition in alphabetic order. Once you close one, the next one is opened.