how append the result in the original .txt file ?

Question

[shreyasarkar0]

hello , i have a .txt file, containing 75 fasta sequences along with their identifier in a .txt file. the functions I have used are extractAAC and extractDC , now I want the result of these two function to get appended in the original text file without creating any duplication. please help.

[Fabio Marroni]

I suggest that you add some info, so that people can help you better: 1) extractAAC and extractDC, from what package? 2) Please provide a small example of your input and of your desired output.