I tried to read some Systeminfos and put into variables:
df -k | grep /dev/mmcblk0p1 | IFS=" " read -r device blocks used available use_percent mounted_on
but did not work, all variables are emty...
The issue is not the IFS, it's because in bash (and certain other shells) the RHS of a pipeline is executed in a subshell.
A simple alternative is to use process substitution to keep the
read in the parent shell:
read -r device blocks used available use_percent mounted_on < <(df -k | grep /dev/mmcblk0p1)