I'm completing the following for one of my assignments using Korn shell.
For each argument in the argument list (which becomes the current pathname):
Check whether the current pathname is a directory, and if so:
Initialize a variable maxsubdir with the null (empty) string, and
a maxentries variable to 0;
For each entry in the directory check if that entry represents a
directory and if so, find the numbers of entries in that
subdirectory with a pipe consisting of ls -l and wc, and save the
result in a variable named curentries.
Compare curentries with maxentries, and if curentries is greater,
update maxsubdir and maxentries. (--10 points)
When the for cycle for a directory is completed, display (with
echo) the directory name, maxsubdir and maxentries (with appropriate
explanatory text.)
If the pathname in a) is not a directory, display the pathname
and an explanatory text saying that the pathname does not represent
a directory.
Go to the next command line argument (pathname) and repeat 1-7
The execution of the script ends when all pathnames are processed (the while is completed )
This is the code I have for it so far (EDITED):
#!/bin/ksh
directoy=$1
while [ $# -ne 0 ]; do
if [ -d $1 ]; then
maxsubdir=
maxentries=0
for x in $1; do
echo "Checking if $1 represents a directory..\n"
curentries="ls -l | wc"
if [ $curentries > $maxentries ]; then
maxentries=$curentries
maxsubdir=$curentries
fi;
done
echo "The directory structure of $1 is … \n"
echo "Maximum sub directories: \n"
echo "$maxsubdir\n"
echo "Maximum directory entries: \n"
echo "$maxentries"
fi
done
Where do I need to insert the "shift" command since I Unix can only handle a limited number of arguments?
Is my syntax appropriate? Or do I have syntax errors on sort lines?
Script seems to run but does not produce output to screen? Perhaps it's endless?
Have a look here and see if this helps out. Explanations are in the code.
#!/bin/ksh
directory=$1
# check whether the entered path is a directory
if [ -d $1 ];then # yes, it's a directory
maxsubdir=null
maxentries=0
echo "$1 is a directory"
# you are only counting lines, add -l to wc
# also you have to not count the first line. it's returns the size
curentries=`ls -l $1 | wc -l`
echo ${curentries}
fi
You don't.
You do have some errors.
Or perhaps, it never reaches that code?
Your assignment says specifically to use a for loop, and you've implemented a while loop.
I'll get you started:
for directory in $*; do
cd "$directory"
curentries=$(ls -1 | wc -l)
for entry in $(ls -1); do
...
done
done
Related
I want to remove the extension of specific files with a given extension.
So for instance, in a directory foobar, we have foo.txt, bar.txt foobar.jpg.
Additionally, the extension that I've put in to be removed is txt
After calling the program, my output should be foo bar foobar.jpg
Here is my code so far:
#!/bin/bash
echo "Enter an extension"
read extension
echo "Enter a directory"
read directory
for file in "$directory"/*; do //
if [[ $file == *.txt ]]
then
echo "${file%.*}"
else
echo "$file"
fi
done
However when I run this on a given directory, nothing shows up.
I'm assuming that there is a problem with how I referred to the directory ( in the line where I placed a //) and I've tried to research on how to solve it but to no avail.
What am I doing wrong?
If files do exist in a valid directory you've entered then they should show up — with one exception. If you are using ~/ (shorthand home directory) then it will be treated as plain text in your for loop. The read variable should be substituted into another variable so the for loop can treat it as a directory (absolute paths should work normally as well).
#!/bin/bash
echo "Enter an extension"
read -r extension
echo "Enter a directory"
read -r directory
dir="${directory/#\~/$HOME}"
for file in "$dir"/*; do
if [[ $file == *."$extension" ]]
then
echo "${file%.*}"
else
echo "$file"
fi
done
You can simplify your for-loop:
for file in "$directory"/*; do
echo "${f%.$extension}";
done
The % instructions removes only matching characters. If nothing matches, the original string (here f) is returned.
When you write bash scripts it's more common to pass arguments to your script via command line arguments rather than by reading it from standard input via read program.
Passing arguments via command line:
#!/bin/bash
# $# - a bash variable which holds a number of arguments passed
# to script via command line arguments
# $0 holds the name of the script
if [[ $# -ne 2 ]]; then # checks if exactly 2 arguments were passed to script
echo "Usage: $0 EXTENSION DIRECTORY"
exit -1;
fi
echo $1; # first argument passed to script
echo $2; # second arugment passed to script
This approach is more efficient because a subprocess is spawn for read command to run and there is no subprocess spawn for reading command line arguments.
There is no need to manually loop through directory, you can use find command to find all files with given extension within given directory.
find /path/to/my/dir -name '*.txt'
find $DIRECTORY -name "*.$EXTENSION"
# note that single quotes in this context would prevent $EXTENSION
# variable to be resolved, so double quotes are used " "
# find searches for files inside $DIRECTORY and searches for files
# matching pattern '*.$EXTENSION'
Note that to avoid bash filename expansion sometimes it is required to wrap actual pattern in single quotes ' ' or double quotes " ". See Bash Filename Expansion
So now your script can look like this:
#!/bin/bash
if [[ $# -ne 2 ]]; then
echo "Usage: $0 EXTENSION DIRECTORY"
exit -1;
fi
$EXTENSION = $1 # for better readability
$DIRECTORY = $2
for file in `find $DIRECTORY -name "*.$EXTENSION"`; do
mv $file ${file%.$EXTENSION}
done
Construct ${file%.$EXTENSION} is called Shell Parameter Expansion it searches for occurrence of .$EXTENSION inside file variable and deletes it.
Notice that in the script it is easy to pass extension as directory and vice versa.
We can check if second argument is in fact directory, we can use following construction:
if ! [[ -d $DIRECTORY ]]; then
echo $DIRECTORY is not a dir
exit -1
fi
This way we can exit from the script earlier with more readable error.
To sum up entire script could look like this:
#!/bin/bash
if [[ $# -ne 2 ]]; then
echo "Usage: $0 EXTENSION DIRECTORY"
exit -1;
fi
EXTENSION=$1 # for better readability
DIRECTORY=$2
if ! [[ -d $DIRECTORY ]]; then
echo $DIRECTORY is not a directory.
exit -1
fi
for file in `find $DIRECTORY -name "*.$EXTENSION"`; do
mv $file ${file%.$EXTENSION}
done
Example usage:
$ ./my-script.sh txt /path/to/directory/with/files
I wrote a small script which:
prints the content of a file (generated by another application) on paper with a matrix printer
prints the same line into a backup file
removes the original file.
The script runs every minute by a cronjob and works fine as long as there are files to print. If there are no files to print, it prints an empty line on the matrix printer and in the backup file. I don't understand why this happens as i implemented an if statement which checks if there is a file to print before the print command is executed. This behaviour only happens if the script is executed by the cron and not if i execute it manually with ./script.sh. What's the reason of this? and how can i solve it?
Something i noticed on the side is that if I place an echo "hi" command in the script, its printed to the matrix printer and the backup file. I expected that its printed to the console console when it has no >> something behind. How does this work?
The script:
#!/bin/bash
# Make sure the backup directory exists
if [ ! -d /home/user/backup_logprint ]
then
mkdir /home/user/backup_logprint
fi
# Print the records if there are any
date=`date +%Y-%m-%d`
filename='_logprint_backup'
printer_path="/dev/usb/lp0"
if [ `ls /tmp/ | grep logprint | wc -l` -gt 0 ]
then
for f in `ls /tmp | grep logprint`
do
echo `cat /tmp/$f` >> "/home/user/backup_logprint/$date$filename"
echo `cat /tmp/$f` >> $printer_path
rm "/tmp/$f"
done
fi
There's no need for ls or an if statement. Just use a proper glob in the for loop, and if no file match, the loop won't be entered.
#!/bin/bash
# Don't check first; just let mkdir decide if
# anything actually needs to be created.
d=/home/user/backup_logprint
mkdir -p "$d"
filename=$(date +"$d/%Y-%m-%d_logprint_backup")
printer_path="/dev/usb/lp0"
# Cause non-matching globs to expand to an empty
# sequence instead of being treated literally.
shopt -s nullglob
for f in /tmp/*logprint*; do
cat "$f" > "$printer_path" && mv "$f" "$d"
done
How to write a bash shell script called 'abc' which takes one argument, the name of a directory, and adds the extension ".xyz" to all visible files in the directory that don't already have it
I have mostly written the code which changes the filenames inside the current directory but I can't get the script to accept an argument (directory name) and change the filenames of that directory
#!/bin/bash
case $# in
0) echo "No directory name provided" >&2 ; exit 1;;
1) cd "${1}" || exit $?;;
*) echo "Too many parameters provided" >&2 ; exit 1;;
esac
for filename in *
do
echo $filename | grep "\.xyz$"
if [ "$?" -ne "0" ]
then mv "$filename" "$filename.old"
fi
done
additional instructions include;
Within 'abc', use a "for" control structure to loop through all the non-hidden filenames
in the directory name in $1. Also, use command substitution
with "ls $1" instead of an ambiguous filename, or you'll descend into subdirectories.
EDIT: The top part of the question has been answered below, however the second part requires me to modify my own code according to the following instructions:
Modify the command substitution that's being used to create the loop values that will be placed into the "filename" variable. Instead of just an "ls $1", pipe the output into a "grep". The "grep" will search for all filenames that DO NOT end in ".xyz". This can easily be done with the "grep -v" option. With this approach, you can get rid of the "echo ... | grep ..." and the "if" control structure inside the loop, and simply do the rename.
How would I go about achieving this because according to my understanding, the answer below is already only searching through filenames without the .xyz extension however it is not being accepted.
Your description is a little unclear in places, so I've gone with the most obvious:
#!/bin/bash
# validate input parameters
case $# in
0) echo "No directory name provided" >&2 ; exit 1;;
1) cd "${1}" || exit $?;;
*) echo "Too many parameters provided" >&2 ; exit 1;;
esac
shopt -s extglob # Enables extended globbing
# Search for files that do not end with .xyz and rename them (needs extended globbing for 'not match')
for filename in !(*.xyz)
do
test -f && mv "${filename}" "${filename}.xyz"
done
The answer to the second part is this:
#!/bin/bash
for file in $(ls -1 "$1" | grep -v '\.old$'); do
mv "$file" "$file.old"
done
I got it from somewhere
I have put the following together with a couple of other articles but it does not seem to be working. What I am trying to do eventually do is for it to check the directory size and then if the directory has new content above a certain total size it will then let me know.
#!/bin/bash
file=private/videos/tv
minimumsize=2
actualsize=$(du -m "$file" | cut -f 1)
if [ $actualsize -ge $minimumsize ]; then
echo "nothing here to see"
else
echo "time to sync"
fi
this is the output:
./sync.sh: line 5: [: too many arguments
time to sync
I am new to bash scripting so thank you in advance.
The error:
[: too many arguments
seems to indicate that either $actualsize or $minimumsize is expanding to more than one argument.
Change your script as follows:
#!/bin/bash
set -x # Add this line.
file=private/videos/tv
minimumsize=2
actualsize=$(du -m "$file" | cut -f 1)
echo "[$actualsize] [$minimumsize]" # Add this line.
if [ $actualsize -ge $minimumsize ]; then
echo "nothing here to see"
else
echo "time to sync"
fi
The set -x will echo commands before attempting to execute them, something which assists greatly with debugging.
The echo "[$actualsize] [$minimumsize]" will assist in trying to establish whether these variables are badly formatted or not, before the attempted comparison.
If you do that, you'll no doubt find that some arguments will result in a lot of output from the du -m command since it descends into subdirectories and gives you multiple lines of output.
If you want a single line of output for all the subdirectories aggregated, you have to use the -s flag as well:
actualsize=$(du -ms "$file" | cut -f 1)
If instead you don't want any of the subdirectories taken into account, you can take a slightly different approach, limiting the depth to one and tallying up all the sizes:
actualsize=$(find . -maxdepth 1 -type f -print0 | xargs -0 ls -al | awk '{s += $6} END {print int(s/1024/1024)}')
I never used shell script, but now I have to , here is what I'm trying to do :
#!/bin/bash
echo running the program
./first
var = ($(ls FODLDER |wc -l)) #check how many files the folder contains
echo $var
if( ["$var" -gt "2"] #check if there are more the 2file
then ./second
fi
the scriopt crashes at the if statement. how may I solve this
Many:
var = ($(ls FODLDER |wc -l))
This is wrong, you cannot have those spaces around =.
if( ["$var" -gt "2"]
Your ( is not doing anything there, so it has to be deleted. Also, you need spaces around [ and ].
All together, this would make more sense:
#!/bin/bash
echo "running the program"
./first
var=$(find FOLDER -maxdepth 1 -type f|wc -l) # better find than ls
echo "$var"
if [ "$var" -gt "2" ]; then
./second
fi
Note:
quote whenever you echo, specially when handling variables.
see another way to look for files in a given path. Parsing ls is kind of evil.
indent your code for better readibility.
Edit your script.bash file as follow:
#!/bin/env bash
dir="$1"
echo "running the program"
./first
dir_list=( $dir/* ) # list files in directory
echo ${#dir_list[#]} # count files in array
if (( ${#dir_list[#]} > 2 )); then # test how many files
./second
fi
Usage
script.bash /tmp/
Explaination
You need to learn bash to avoid dangerous actions!
pass the directory to work with as first argument in the command line (/tmp/ → `$1)
use glob to create an array (dir_list) containing all file in given directory
count items in array (${#dir_list[#]})
test the number of item using arithmetic context.