To show previously executed commands use the history command
history
history
865 find / -name 'file1.txt' 2> errors.txt
866 cat errors.txt
867 ll
868 ls errors.txt
869 ll errors.txt
870 source .bashrc
871 ll errors.txt
872 ls -lah errors.txt
# It includes the executed commands and the history number associated to them
history | less
# To execute one of the previous commands use !HISTORY_NUMBER
!868
# To execute the last command use these shortcuts
!-1
!!
# Up & Down arrow keys can be used to scroll through history
# To execute the last "command" command - cat for example
!cat
The configuration options of the history are located in the .bashrc file
cat ~/.bashrc
# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000
Command Substitution
Redirecting doesn't always work.
With command substitution a command can be replaced with its output before the entire command is executed by the shell.
Backticks `` or $() are used:
ls -l `cat file.txt`
ls -l $(cat file.txt)
# Example with a file list
cat file-list.txt
file1.txt
file2.txt
file3.txt
ls -l `cat file-list.txt`
-rw-rw-r-- 1 root root 6 set 3 00:16 file1.txt
-rw-rw-r-- 1 user user 7 set 3 00:16 file2.txt
-rw-rw-r-- 1 user user 8 set 3 00:16 file3.txt
