In many cases, you would want to see what is in a text file or edit a file, or create one from scratch. There are multiple ways to view the files.
cat will print the whole content of the text file to your shell, if you don't redirect the output to another file. Here is how it works:
$ cat log.txt AD 123 AA 233 Ad 443 $
If you would like to display only the beginning of a file or the end, you can use
head shows the beginning and
tail the end. Here we look at beginning and the end of
example.fastq file, which contains reads from a next-generation sequencing experiment.
$ head example.fastq @DJG60NM1:206:C2L3LACXX:1:1101:1934:1996 1:N:0:GCCAAT NTTTGTAGAACCTTTTGTAATTCTGCTTATATTGGTAGCCAATGCAATTGT + #1=DFFFFHHHHHIJJIIIIJJFIJJJJIJJJJIIIJJIJJIJIJJIIJJG @DJG60NM1:206:C2L3LACXX:1:1101:2193:1996 1:N:0:GCCAAT NGAATCACCCCTTTAAATCCCCTAGAAGTACCCCTTCTAAATACATCAGTC + #1=DDDFFHHHHHJIIJIJIJJGIGIHI?FHGIJIJIJIJIFIEEIGJBBE @DJG60NM1:206:C2L3LACXX:1:1101:2277:1999 1:N:0:GCCAAT NTTTAATAATGCGCTCCCCAAACAGAACAGCACCACCACTGGGGTCTCCGT $ $ $ tail example.fastq @DJG60NM1:206:C2L3LACXX:1:1101:2023:1996 1:N:0:CAGATC NTTGAAGTTAAATTTGGGAACTCATAGGAAATAAAGGAGCATGAACCAAGG + #1=DDDFFHHHHHJJIJJIJJJJIJJJJIIJJJJJJJJJJJJIJJJJJJJI @DJG60NM1:206:C2L3LACXX:1:1101:2057:2000 1:N:0:CAGATC NGGTTGGTGGGCTGATGTCTATAAGTACTAGGGTAGCTCCTCCGATTAGAT + #1:4ABDDDDD?D@DEEEBFFFEIEEBBEDD;BC?DEDEBBDDD6BD@B8B @DJG60NM1:206:C2L3LACXX:1:1101:2305:1999 1:N:0:CAGATC NGTATTTCATGTGGTATAAGCATCTGGATAATCAGAGTAACGACGAGGTAT
In some cases, you may want to look at a large file page by page. If you use
cat, the whole file will be printed at once. It is inconvenient to use that if you want to inspect a large file. Instead you can use
less, to view the files page by page.
echo command prints the argument on the shell. See the following example.
$ echo hello world hello world $ $ echo here it is here it is
However, you can also use echo to write files using
>. When you finish typing just add
> filename.txt and the output will be written on
$ echo hello world > myfile.txt $ $ cat myfile.txt hello world $
Emacs is a text editor that you can invoke using
emacs shell command. It is a powerfull text editor used by programmers and system adminstrators to create and manipulate text file, as well as, writing programs. Detailed introductions to emacs is beyond the scope of this document, but you can follow this link to learn more about emacs.
You can open a text document using
emacs filename command. Once emacs is started, you can type the content of the text file using your keyboard and save the file using
C-x C-s, which means you have to type Ctrl+x then Ctrl+s, and your file will be saved. You can quit an emacs session using