remove the first line of all files

Shell Programming and Scripting
1

I want to remove the first line of all files in a directory with .dat extension. Can any one help me on this with a small script. I want the file names to remain same .

2 
ls *dat|xargs -i ksh -c 'sed -e "1d" {}>{}.tmp;mv {}.tmp {}'
3

stty: : No such device or address

4

you can use

# tail +2 file.dat > newfile

or

# more +2 file.dat > newfile

to get 2nd line of file onwards. I leave it to you to do the rest. Try.

5

Just for fun:

awk 'FNR != 1  { print >>FILENAME".tmp";next}
    { print FILENAME 
       ">"FILENAME".tmp" }' *dat|xargs -i mv "{}.tmp" "{}"
6

for files in `ls *.dat` #list of all .dat file
do
cp $files $files.bck #make a backup of the file
sed '1d' -i $files #remove the first line of the file
done

Rakesh UV

7

just for fun: for very large files, use awk/more instead of sed '1d' method.

# wc -l file1
8998841 file1
# time sed '1d' file1 > sedtest

real    0m28.329s
user    0m26.930s
sys     0m1.000s
# time sed -n '2,$p' file1 > sedtest

real    0m33.740s
user    0m29.842s
sys     0m1.096s

# time more +2 file1 > moretest

real    0m10.629s
user    0m8.353s
sys     0m0.856s
 # time awk 'NR>1' file1 > awktest

real    0m14.618s
user    0m7.476s
sys     0m1.016s
8

Good point ghostdog

9

more command seems to yield the better performance on the overall