What is a unix command for deleting the first N characters of a line?
BashUnixCommandTruncateBash Problem Overview
For example, I might want to:
tail -f logfile | grep org.springframework | <command to remove first N characters>
I was thinking that tr might have the ability to do this but I'm not sure.
Bash Solutions
Solution 1 - Bash
Use cut. Eg. to strip the first 4 characters of each line (i.e. start on the 5th char):
tail -f logfile | grep org.springframework | cut -c 5-
Solution 2 - Bash
sed 's/^.\{5\}//' logfile
and you replace 5 by the number you want...it should do the trick...
EDIT
if for each line sed 's/^.\{5\}//g' logfile
Solution 3 - Bash
You can use cut:
cut -c N- file.txt > new_file.txt
-c: characters
file.txt: input file
new_file.txt: output file
N-: Characters from N to end to be cut and output to the new file.
Can also have other args like: 'N' , 'N-M', '-M' meaning nth character, nth to mth character, first to mth character respectively.
This will perform the operation to each line of the input file.
Solution 4 - Bash
tail -f logfile | grep org.springframework | cut -c 900-
would remove the first 900 characters
cut uses 900- to show the 900th character to the end of the line
however when I pipe all of this through grep I don't get anything
Solution 5 - Bash
I think awk would be the best tool for this as it can both filter and perform the necessary string manipulation functions on filtered lines:
tail -f logfile | awk '/org.springframework/ {print substr($0, 6)}'
or
tail -f logfile | awk '/org.springframework/ && sub(/^.{5}/,"",$0)'
Solution 6 - Bash
Here is simple function, tested in bash. 1st param of function is string, 2nd param is number of characters to be stripped
function stringStripNCharsFromStart { echo ${1:$2:${#1}} }
Usage:
Solution 7 - Bash
x=hello
echo ${x:1}
returns ello
replace 1 with N as required