15 Linux Split and Join Command Examples to Manage Large Files--reference
by on OCTOBER 16, 2012
http://www.thegeekstuff.com/2012/10/15-linux-split-and-join-command-examples-to-manage-large-files/
Linux split and join commands are very helpful when you are manipulating
large files. This article explains how to use Linux split and join command with
descriptive examples.
Join and split command syntax:
join [OPTION]… FILE1 FILE2
split [OPTION]… [INPUT [PREFIX]]
Linux Split Command Examples
1. Basic Split Example
Here is a basic example of split command.
$ split split.zip $ ls split.zip xab xad xaf xah xaj xal xan xap xar xat xav xax xaz xbb xbd xbf xbh xbj xbl xbn xaa xac xae xag xai xak xam xao xaq xas xau xaw xay xba xbc xbe xbg xbi xbk xbm xbo
So we see that the file split.zip was split into smaller files with x** as file names. Where ** is the two character suffix that is added by default. Also, by default each x** file would contain 1000 lines.
$ wc -l *
40947 split.zip
1000 xaa
1000 xab
1000 xac
1000 xad
1000 xae
1000 xaf
1000 xag
1000 xah
1000 xai
...
...
...
So the output above confirms that by default each x** file contains 1000 lines.
2.Change the Suffix Length using -a option
As discussed in example 1 above, the default suffix length is 2. But this can be changed by using -a option.
As you see in the following example, it is using suffix of length 5 on the split files.
$ split -a5 split.zip $ ls split.zip xaaaac xaaaaf xaaaai xaaaal xaaaao xaaaar xaaaau xaaaax xaaaba xaaabd xaaabg xaaabj xaaabm xaaaaa xaaaad xaaaag xaaaaj xaaaam xaaaap xaaaas xaaaav xaaaay xaaabb xaaabe xaaabh xaaabk xaaabn xaaaab xaaaae xaaaah xaaaak xaaaan xaaaaq xaaaat xaaaaw xaaaaz xaaabc xaaabf xaaabi xaaabl xaaabo
Note: Earlier we also discussed about other file manipulation utilities – tac, rev, paste.
3.Customize Split File Size using -b option
Size of each output split file can be controlled using -b option.
In this example, the split files were created with a size of 200000 bytes.
$ split -b200000 split.zip $ ls -lart total 21084 drwxrwxr-x 3 himanshu himanshu 4096 Sep 26 21:20 .. -rw-rw-r-- 1 himanshu himanshu 10767315 Sep 26 21:21 split.zip -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xad -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xac -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xab -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xaa -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xah -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xag -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xaf -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xae -rw-rw-r-- 1 himanshu himanshu 200000 Sep 26 21:35 xar ... ... ...
4. Create Split Files with Numeric Suffix using -d option
As seen in examples above, the output has the format of x** where ** are alphabets. You can change this to number using -d option.
Here is an example. This has numeric suffix on the split files.
$ split -d split.zip $ ls split.zip x01 x03 x05 x07 x09 x11 x13 x15 x17 x19 x21 x23 x25 x27 x29 x31 x33 x35 x37 x39 x00 x02 x04 x06 x08 x10 x12 x14 x16 x18 x20 x22 x24 x26 x28 x30 x32 x34 x36 x38 x40
5. Customize the Number of Split Chunks using -C option
To get control over the number of chunks, use the -C option.
This example will create 50 chunks of split files.
$ split -n50 split.zip $ ls split.zip xac xaf xai xal xao xar xau xax xba xbd xbg xbj xbm xbp xbs xbv xaa xad xag xaj xam xap xas xav xay xbb xbe xbh xbk xbn xbq xbt xbw xab xae xah xak xan xaq xat xaw xaz xbc xbf xbi xbl xbo xbr xbu xbx
6. Avoid Zero Sized Chunks using -e option
While splitting a relatively small file in large number of chunks, its good to avoid zero sized chunks as they do not add any value. This can be done using -e option.
Here is an example:
$ split -n50 testfile $ ls -lart x* -rw-rw-r-- 1 himanshu himanshu 0 Sep 26 21:55 xag -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xaf -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xae -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xad -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xac -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xab -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:55 xaa -rw-rw-r-- 1 himanshu himanshu 0 Sep 26 21:55 xbx -rw-rw-r-- 1 himanshu himanshu 0 Sep 26 21:55 xbw -rw-rw-r-- 1 himanshu himanshu 0 Sep 26 21:55 xbv ... ... ...
So we see that lots of zero size chunks were produced in the above output. Now, lets use -e option and see the results:
$ split -n50 -e testfile $ ls split.zip testfile xaa xab xac xad xae xaf $ ls -lart x* -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xaf -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xae -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xad -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xac -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xab -rw-rw-r-- 1 himanshu himanshu 1 Sep 26 21:57 xaa
So we see that no zero sized chunk was produced in the above output.
7. Customize Number of Lines using -l option
Number of lines per output split file can be customized using the -l option.
As seen in the example below, split files are created with 20000 lines.
$ split -l20000 split.zip
$ ls
split.zip testfile xaa xab xac
$ wc -l x*
20000 xaa
20000 xab
947 xac
40947 total
Get Detailed Information using –verbose option
To get a diagnostic message each time a new split file is opened, use –verbose option as shown below.
$ split -l20000 --verbose split.zip creating file `xaa‘ creating file `xab‘ creating file `xac‘
Linux Join Command Examples
8. Basic Join Example
Join command works on first field of the two files (supplied as input) by matching the first fields.
Here is an example :
$ cat testfile1 1 India 2 US 3 Ireland 4 UK 5 Canada $ cat testfile2 1 NewDelhi 2 Washington 3 Dublin 4 London 5 Toronto $ join testfile1 testfile2 1 India NewDelhi 2 US Washington 3 Ireland Dublin 4 UK London 5 Canada Toronto
So we see that a file containing countries was joined with another file containing capitals on the basis of first field.
9. Join works on Sorted List
If any of the two files supplied to join command is not sorted then it shows up a warning in output and that particular entry is not joined.
In this example, since the input file is not sorted, it will display a warning/error message.
$ cat testfile1 1 India 2 US 3 Ireland 5 Canada 4 UK $ cat testfile2 1 NewDelhi 2 Washington 3 Dublin 4 London 5 Toronto $ join testfile1 testfile2 1 India NewDelhi 2 US Washington 3 Ireland Dublin join: testfile1:5: is not sorted: 4 UK 5 Canada Toronto
10. Ignore Case using -i option
When comparing fields, the difference in case can be ignored using -i option as shown below.
$ cat testfile1 a India b US c Ireland d UK e Canada $ cat testfile2 a NewDelhi B Washington c Dublin d London e Toronto $ join testfile1 testfile2 a India NewDelhi c Ireland Dublin d UK London e Canada Toronto $ join -i testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London e Canada Toronto
11. Verify that Input is Sorted using –check-order option
Here is an example. Since testfile1 was unsorted towards the end so an error was produced in the output.
$ cat testfile1 a India b US c Ireland d UK f Australia e Canada $ cat testfile2 a NewDelhi b Washington c Dublin d London e Toronto $ join --check-order testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London join: testfile1:6: is not sorted: e Canada
12. Do not Check the Sortness using –nocheck-order option
This is the opposite of the previous example. No check for sortness is done in this example, and it will not display any error message.
$ join --nocheck-order testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London
13. Print Unpairable Lines using -a option
If both the input files cannot be mapped one to one then through -a[FILENUM] option we can have those lines that cannot be paired while comparing. FILENUM is the file number (1 or 2).
In the following example, we see that using -a1 produced the last line in testfile1 (marked as bold below) which had no pair in testfile2.
$ cat testfile1 a India b US c Ireland d UK e Canada f Australia $ cat testfile2 a NewDelhi b Washington c Dublin d London e Toronto $ join testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London e Canada Toronto $ join -a1 testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London e Canada Toronto f Australia
14. Print Only Unpaired Lines using -v option
In the above example both paired and unpaired lines were produced in the output. But, if only unpaired output is desired then use -v option as shown below.
$ join -v1 testfile1 testfile2 f Australia
15. Join Based on Different Columns from Both Files using -1 and -2 option
By default the first columns in both the files is used for comparing before joining. You can change this behavior using -1 and -2 option.
In the following example, the first column of testfile1 was compared with the second column of testfile2 to produce the join command output.
$ cat testfile1 a India b US c Ireland d UK e Canada $ cat testfile2 NewDelhi a Washington b Dublin c London d Toronto e $ join -1 1 -2 2 testfile1 testfile2 a India NewDelhi b US Washington c Ireland Dublin d UK London e Canada Toronto
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