Общий способ через sed
[guest@localhost tmp]$ touch file{1,2,3}.txt
[guest@localhost tmp]$
[guest@localhost tmp]$ ls file*.txt
file1.txt file2.txt file3.txt
[guest@localhost tmp]$ ls file*.txt | sed 's%\([^.]*\)\(\.txt\)%mv & \1_save\2%'
mv file1.txt file1_save.txt
mv file2.txt file2_save.txt
mv file3.txt file3_save.txt
[guest@localhost tmp]$ ls file*.txt | sed 's%\([^.]*\)\(\.txt\)%mv & \1_save\2%' | sh
[guest@localhost tmp]$ ls file*.txt
file1_save.txt file2_save.txt file3_save.txt
[guest@localhost tmp]$