Tag: Unix

Nice tips of unix command tools

123   398  17359
317    19    2909
 39  -399   -5789
 49    33      200
255   33     -378

sort -n file 

Sort the file by first column. The -n option ensures numeric (as opposed to lexicographic) sort.

sort -k 2 -n file 

Sort the file by second column. The “-k” option here denotes the column used as sort key.

grep '33' file 

Extract all lines containing the string “33” (in the above example, lines 4 and 5).

grep -c '33' file 

Same, but display only the number of matching lines (2 in the example), not the lines themselves. This is useful to analyze large data files of output data. For example, if a sequence of one million integers, is saved as a file, one per line, “grep -c ’33’ file” will display the number of 0’s in that sequence.

grep -c '-' *.out 

Same command, but applied to all files in the current directory matching “*.out”. For each file there is an output line of the form “Filename: x”, where “x” is the number of matching lines in the file.

sort -n file | cat -n 

Sort the file, then prepend line numbers to each line. This results in the following:

     1	 39  -399  -5789
     2	 49  33   200
     3	123  398  17359
     4	255 33   -378
     5	317  19  2909

http://www.math.uiuc.edu/~hildebr/computer/unixtips.html