How to get some specific lines from huge text file in unix?

Question

I use importing systems based on delimited text files. The files used can sometimes be almost 2 Gb big and I have to check some lines from that file. So I want to know how ca

Answer 1

You can do this with many Unix tools, for instance with awk:

# print first 5 lines with awk
awk 'NR>=1&&NR<=5{print}NR>=6{exit}' file

# print selection of lines 
awk 'NR==994123||NR==1002451||NR==1010123{print}NR>1010123{exit}' file

Answer 2

In python:

readThisFile = open('YOURFILE')
outputFile = open('OUTPUT', w)

for actualline, linetext in enumerate(readThisFile):
    if actualline == WANTEDLINE
        outputFile.write(linetext)
    else:
        pass

If wanted you can modify that script to work with arguments (like getline.py 1234)

Answer 3

To print line N, use:

sed 'Nq;d' file

To print multiple lines (assuming they are in ascending order) e.g. 994123, 1002451, 1010123:

sed '994123p;1002451p;1010123q;d' file

The q after the last line number tells sed to quit when it reaches the 1010123th line, instead of wasting time by looping over the remaining lines that we are not interested in. That is why it is efficient on large files.