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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 can I output (on another file, or just on screen) the lines of specific value? E.g. line number 1010123, 1002451, 994123, etc., exactly as they are in the source file?
981
Using the head and tail Commands The idea is: First, we get line 1 to X using the head command: head -n X input. Then, we pipe the result from the first step to the tail command to get the last line: head -n X input | tail -1.
To do this, press Esc , type the line number, and then press Shift-g . If you press Esc and then Shift-g without specifying a line number, it will take you to the last line in the file. To look for the next occurrence after the first, either press n or press / again and then press Enter .
Grep is a Linux / Unix command-line tool used to search for a string of characters in a specified file. The text search pattern is called a regular expression. When it finds a match, it prints the line with the result. The grep command is handy when searching through large log files.
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.
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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
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