Jesus asks: I have a question about the split Command… How can I “come back” to “largefile” from 126 small files?It sounds like the split command was used? If so, then you can use a for loop with file concatenation. First, I will split the files for my example:

$ ls -l big.log
-rw-rw-r--  1 brock brock 175743061 Oct 11 22:08 big.log
$ expr 175743061 \/ 126
1394786
$ split -b 1394786 big.log
$ ls -1 x*
xaa
xab
...
xew

Split creates its output files in decreasing alphabetic order. Thus when you list them in the shell they are in the order in which
they were split. As such, you can simply use cat to merge the files. (Thanks to Paul and Davidov for pointing out my for loop was superfluous.)

$ cat x* >merged.big.log
$ ls -l *.log
-rw-rw-r--  1 brock brock 175743061 Oct 12 22:08 big.log
-rw-rw-r--  1 brock brock 175743061 Oct 12 01:11 merged.big.log
$ diff merged.big.log big.log
$ md5sum *.log
47de08911534957c1768968743468307  big.log
47de08911534957c1768968743468307  merged.big.log