In this section, we will look at a few more Unix commands for how to access content in files. We are now in the peach directory, in the previous section we looked at more and less. If the file is very long, though, we might only want to see a portion of the file, let's say the portion at the top. The command head, followed by the name of the file, would give us the top ten lines in a file. So you might know this, that in the peach genome, our sequences are named scaffold one and perhaps, scaffold two and so on. Followed by the sequence of a's, c's, g's and d's, the genomic sequence. If I want to change the number of lines that we see from the top of the file, we can do so by specifying head, let's say, -50. Peach.genome, return, and that's going to show us the 50 lines. And similarly, head-20 peach.genome. Obviously, we can use the same command to look at the genes five head peach.genes, which will list the top ten lines. And similarly peach.samples. Now just as an observation as we're exploring this particular file structure, you will see that the peach.genes include among others, shape, smell, taste, and size, and they each of them having a number of variants. And that our experiment only sampled the fruit from the peach. So, head would give us a number of lines from the beginning of the file. Sometimes we might want to extract a number of files to test a particular procedure, rather than use the entire, very large file. In a similar way, we can use tail to look at the last few lines at the end of a file. For instance, those might be some statistics that are attached at the end of the file. So tail peach.genome, in this particular case, would give us the last ten lines, which only show the end of the genomic sequence. We can similarly do tail-15, for instance, to extract the last fifteen lines from the genome file, and we can do so with the genes file. And with a samples file. One last command for accessing content that I want to show you is cat. Cat actually stands for concatenate. So we can concatenate multiple files using cat, or we can simply show the content of one file. So in this case, I'm going to show you the content of the file peach.genes. Catpeach.genes. I'm going change to the parent directory, and now, let's concatenate the content of all the genes files. Cat star, to mark any directory, p star .genes. So as you can see, this put together the content of the genes files across the three directories apple, aeach, and pear. Let's also try to do this with the gnome files, and that went very fast. So when the file is large, cat is going to show the entire content of the file. It is not going to give us the time to stop and look at how it's represented. So perhaps, we need a way of capturing the output from this program so we can view it at our leisure and this is what the next section will be about. So for the time being, this concludes this section on accessing content.
