Writing, publishing, geekdom, and errata.

Bash string padding with SED

technology.pngI know, I mentioned a bit of this earlier, but it deserves its own post.

You can left and right pad strings in BASH with spaces using SED. You do not have to use printf or anything else (despite what everyone else says).(Derived from instructions here, which talk more about centering than padding.)

This is the important part of the code:
Left justify with string length of 80
sed -e :a -e 's/^.\{1,80\}$/& /;ta'
Right justify with string length of 80
sed -e :a -e 's/^.\{1,80\}$/ &/;ta'
Center with string length of 80.
sed -e :a -e 's/^.\{1,80\}$/ & /;ta'


Pureferret said...

Would it be possible to use this technique to convert from exponential notation to decimal?

e.g convert 1.3e-2 ->0.013

Steve Saus said...

Honestly, I have no idea. I often have to use a "try, try again" approach to SED.

I'd think AWK might be a more useful tool for that, though - and perhaps a little easier to understand.

tocororo-macho said...

Thanks for your post, I have crated a small function to make it reusable for scripting.

function padding () {
CONTENT="${1}"; PADDING="${2}"; LENGTH="${3}"; TRG_EDGE="${4}";
case "${TRG_EDGE}" in
left) echo ${CONTENT} | sed -e :a -e 's/^.\{1,'${LENGTH}'\}$/&\'${PADDING}'/;ta'; ;;
right) echo ${CONTENT} | sed -e :a -e 's/^.\{1,'${LENGTH}'\}$/\'${PADDING}'&/;ta'; ;;
center) echo ${CONTENT} | sed -e :a -e 's/^.\{1,'${LENGTH}'\}$/'${PADDING}'&'${PADDING}'/;ta'
return ${RET__DONE};

Usage: echo "IP Address: `padding "${IP_ADDRESS}" "${PADDING}" ${LENGTH}`webserver";
Hope you find it of any use.

Beatrice Prose said...

In the end, I found this post !

Thank YOU !