Write a Shell script to simulate the 'tree' command
August 3, 2014
shell
I wrote a shell script to simulate the ‘tree’ tool in Linux.
This is the code:
#!/bin/bash -
#===============================================================================
#
# FILE: RecursiveDir.sh
#
# USAGE: bash RecursiveDir.sh [directory] [longest deepth] [empty]
#
# DESCRIPTION: This script can list the files and dirs
# recursively in the current directory
# if empty argument is set to "empty", it will print a empty line
# before and after a directory
#
# OPTIONS: longest_deepth is set to 4 by default
# directory is set to current directory by default
# empty argument is set to "n" by default
# REQUIREMENTS: ---
# BUGS: ---
# NOTES: It print a empty line after a directory
# AUTHOR: liuxueyang (lxy), liuxueyang457@163.com
# ORGANIZATION: Hunan University
# CREATED: 08/02/2014 20:52
# REVISION: ---
#===============================================================================
set -o nounset # Treat unset variables as an error
# this function used to print a empty line before or after a directory
printempty()
{
if [ $empty = "empty" ]; then
NumberOfVeri=$[${#tab}/2+1]
count=0
while [ $count -lt $NumberOfVeri ]
do
echo -n $veri
echo -n ' ' # This is 7 spaces
count=$[$count+1]
done
echo
fi
}
# This function is recursive
# It lists the files and directories in the current dir
recdir()
{
tab=$tab$singletab
# to test whether the deepth is greater than required
if [ ${#tab} -gt $nu ]
then
## Note that we must delete a tab before we go upper directory!
tab=${tab%"\t"}
return
fi
for file in "$@"
do
# echo -en $tab$file
# minus_tab=${tab%"\t"}
# echo -en $minus_tab
# print vertical lines
NumberOfVeri=$[${#tab}/2-1]
count=0
while [ $count -lt $NumberOfVeri ]
do
echo -n $veri
echo -n ' ' # This is 7 spaces
count=$[$count+1]
done
echo -n $veri
# print horizonal lines
count=0
while [ $count -lt 7 ]
do
echo -n "-"
count=$[$count+1]
done
echo -n $file
# we get the path from original directory of the current file
# or directory
thisfile=$thisfile/$file
if [ -d "$thisfile" ]
then
echo /
# add empty line before a directory begins
printempty
# we force 'ls' to be a builtin command instead of some function
# or alias that we create by ourself
recdir $(command ls $thisfile)
# add an empty line after a directory ends
printempty
else
echo
fi
# we must set thisfile to be the current directory
thisfile=${thisfile%/*}
done
# we delete a tab when we get to the upper directory
tab=${tab%"\t"}
}
# This function init
recls()
{
tab=""
singletab="\t"
list=$(ls $1)
for tryfile in $list #### HERE! WE CAN NOT WRITE "$list" or shell will
#### treat it as one variable!!!!
#### I deserve it! :-(
do
echo -n $tryfile
## fix a BUG in book:
## we add $1 in order to use any available directory
## instead of only current directory of the script path
tryfile=$1/$tryfile
if [ -d $tryfile ]
then
echo /
# add empty line before a directory begins
printempty
thisfile=$tryfile
recdir $(command ls $tryfile)
# add an empty line after a directory ends
printempty
else
echo
fi
done
# we unset these variables cause we do not use them
# By the way, in order not to overwrite system command
# in some other script it is better to do this.
unset dir singletab tab
}
result=${1:-"."}
nu=${2:-4}
nu=$[($nu-1)*2]
empty=${3:-"n"}
# this two variable are used to draw
hori="-"
veri="|"
recls $result
exit 0
My script accepts 3 arguments.
The first argument is the directory you want to show. It is set by the same directory as the where the script locates.
The second argument is the Longest depth of the tree. It means that the deepest path you want to see. If there are more deep directory, it will not list the directory instead it will just list the directory’s name. Besides, it is set as 4 by default.
The third argument is set by “empty” by default which means that you want to show an empty line before a directory begins and ends. If you omit the argument, it will not show that. I think it looks better without those empty lines. ;-)
This exercise is from the book Learning the bash Shell. Maybe the algorithm is not quite difficult. However, I made a lot of mistakes and debugged a lot before the script ran well when I am not very good at the grammar of shell script.
Here are some examples:
Example 1:
~>./RecursiveDir.sh tmpdir
a0.cpp
b1.cpp
c2.cpp
d3.cpp
tm1/
|-------a.c
|-------tm2/
| |-------b.c
| |-------tm3/
| | |-------c.dd
| |-------z.cc
~>tree tmpdir/
tmpdir/
├── a0.cpp
├── b1.cpp
├── c2.cpp
├── d3.cpp
└── tm1
├── a.c
└── tm2
├── b.c
├── tm3
│ └── c.dd
└── z.cc
3 directories, 8 files****
Example 2:
I set the second argument. We can see that the "tm3" directory is not listed in detail.
~>./RecursiveDir.sh tmpdir 3
a0.cpp
b1.cpp
c2.cpp
d3.cpp
tm1/
|-------a.c
|-------tm2/
| |-------b.c
| |-------tm3/
| |-------z.cc
Example 3:
I set the third argument to empty. We can see empty lines when a directory begins and ends.
~>./RecursiveDir.sh tmpdir 5 empty
a0.cpp
b1.cpp
c2.cpp
d3.cpp
tm1/
|
|-------a.c
|-------tm2/
| |
| |-------b.c
| |-------tm3/
| | |
| | |-------c.dd
| | |
| |-------z.cc
| |
|