I don't if this method is applicable or not.
#!/bin/bash
file=$1
if [[ -x "$file" ]]
then
if [ $? = 0 ]
then
echo $file is executable
else
echo $file is not executable
fi
fi
But if i run this script with a non executable file it returns nothing
But if i run this script with a executable file it returns "name is executable"
just want to know about positional parameter working. i'm a beginner.but can i
take the output of the first if condition into $?
For such test you do not need the internal if. THis code will do the work:
#!/bin/bash
file=$1
if [[ -x "$file" ]]
then
echo $file is executable
else
echo $file is not executable
fi
Related
How do i create a script to check for the file is hidden or not?
#!/bin/bash
FILE="$1"
if [ -f "$FILE" ];
then
echo "File $FILE is not hidden."
else
echo "File $FILE is hidden" >&2
fi
but it is unable to do so. Please help me.
Check if the filename begins with .:
file=$1
base=$(basename "$file")
if [[ $base == .* ]]
then echo "File $file is hidden"
else echo "File $file is not hidden"
fi
You essentially have to check if filename starts with . (period).
filename=$(basename -- "$FILE")
Then you have to use pattern matching
if [[ $filename == .* ]]
then
# do something
fi
The test command would be:
[[ "${file##*/}" == .* ]]
It's necessary to remove the path, to see if file name starts with .. Here I used prefix removal. It's the most efficient, but will choke if a file contains slashes (very unlikely, but be aware).
A full script should include a test that the given file actually exists:
#!/bin/bash
file=$1
[[ -e "$file" ]] && { echo "File does not exist: $file" >&2; exit 1; }
if [[ "${file##*/}" == .* ]]; then
echo "Hidden: $file"
else
echo "Not hidden: $file"
fi
You could also list all hidden files in a directory:
find "$dir" -name .\*
Or all not hidden files:
find "$dir" -name '[^.]*'
Depending on the task, it's probably better to use a list of hidden or not hidden files, to work on.
Also, by default, ls does not list hidden files. Unless you use -a.
I need to make a bash script that checks if the file or directory exists,then if the file does,it checks the executable permission.I need to modify the script to be able to give a file executable permissions from an argument.
Example: Console input ./exist.sh +x file_name should make the file executable.
This is the unfinished code that checks if the file/directory exists and if the file is executable or not. I need to add the chmod argument part.
#!/bin/bash
file=$1
if [ -x $file ]; then
echo "The file '$file' exists and it is exxecutable"
else
echo "The file '$file' is not executable (or does not exist)"
fi
if [ -d $file ]; then
echo "There is a directory named '$file'"
else
echo "There is no directory named '$file'"
fi
If you have optional arguments to your script, you need to check for them first.
In the case of just a couple of simple arguments, it would be simpler to check for them explicitly.
MAKEEXECUTABLE=0
while [ "${1:0:1}" = "+" ]; do
case $1 in
"+x")
MAKEEXECUTABLE=1
shift
;;
*)
echo "Unknown option '$1'"
exit
esac
done
file=$1
Then after you have determined that the file is not executable
if [ $MAKEEXECUTABLE -eq 1 ]; then
chmod +x $file
fi
Should you decide to add more complex options, you may want to use something like getops:example of how to use getopts in bash
Add chmod something like:
if [ ! -x "$file" ]; then
chmod +x $file
fi
This means if file does not have execute persmission, then add execute permission for the user.
I'm trying to run programs (for example mv file1.txt file2.txt) in my .sh script and I need to hide errors, but handle it with my script.
Currently I'm trying to do something like
EXECUTE="mv -v $VOL $BACKUP_YESTERDAY_CRYPT"
{
EXEC_ERROR=$($EXECUTE)
} &2>> $LOG_FILE
if [[ -n $EXEC_ERROR ]]; then
echo "There is an error!"
fi
But it doesn't work at all - it shows an error (for example mv: cannot stat 'file1.txt': No such file or directory) and $EXEC_ERROR variable is empty.
Is there any way to get output to variable + to log file?
How about something like:
mv -v $VOL $BACKUP_YESTERDAY_CRYPT 2>> $LOG_FILE
if [[ ! ( $? -eq 0 ) ]] ; then
echo "There is an error\!"
fi
Though $? is good for saving and processing exit codes, the if statement is designed to take any command, not just [ or [[:
if ! mv -v "$VOL" "$BACKUP_YESTERDAY_CRYPT" 2>> $LOG_FILE; then
echo "There is an error!"
fi
This includes saving variables:
if OUTPUT=$(mv -v "$VOL" "$BACKUP_YESTERDAY_CRYPT" 2>> $LOG_FILE); then
echo ">>> $OUTPUT <<<"
fi
In fact, if can take more than one command, as its man page describes. Documentation on boolean operators such as !, &&, and || is hidden within the description of shell commands, where they form pipelines (!) and lists (&&, ||).
Try this:
mv sourcefile destfile 2> /dev/null 1>logfile
returnstatus=`echo $?`
if [[ $returnstatus -ne 0 ]]; then
echo "There was an error!"
fi
I'm trying to create a script that searches through a directory to find symlinks that point to non-existing objects.
I have a file in a directory with a deleted symlink, but for some reason when i run the below script It says file exists.
#!/bin/bash
ls -l $1 |
if [ -d $1 ]
then
while read file
do
if test -e $1
then
echo "file exists"
else
echo "file does not exist"
fi
done
else
echo "No directory given"
fi
Thanks
Check this page. It has a test for broken links. It uses the -h operator to identify a symlink and the -e operator to check existance.
From that page:
linkchk () {
for element in $1/*; do
[ -h "$element" -a ! -e "$element" ] && echo \"$element\"
[ -d "$element" ] && linkchk $element
# Of course, '-h' tests for symbolic link, '-d' for directory.
done
}
# Send each arg that was passed to the script to the linkchk() function
#+ if it is a valid directoy. If not, then print the error message
#+ and usage info.
##################
for directory in $directorys; do
if [ -d $directory ]
then linkchk $directory
else
echo "$directory is not a directory"
echo "Usage: $0 dir1 dir2 ..."
fi
done
exit $?
You can test whether link is valid or not using:
[[ -f "$link" ]] && echo "points to a valid file"
To check if it is indeed a link use -L:
[[ -L "$link" ]] && echo "it's a link"
There seems to be a program named symlinks that does, among other things, what you're looking for.
As arguments to my script there are some file paths. Those can, of course, be relative (or contain ~). But for the functions I've written I need paths that are absolute, but do not have their symlinks resolved.
Is there any function for this?
MY_PATH=$(readlink -f $YOUR_ARG) will resolve relative paths like "./" and "../"
Consider this as well (source):
#!/bin/bash
dir_resolve()
{
cd "$1" 2>/dev/null || return $? # cd to desired directory; if fail, quell any error messages but return exit status
echo "`pwd -P`" # output full, link-resolved path
}
# sample usage
if abs_path="`dir_resolve \"$1\"`"
then
echo "$1 resolves to $abs_path"
echo pwd: `pwd` # function forks subshell, so working directory outside function is not affected
else
echo "Could not reach $1"
fi
http://www.linuxquestions.org/questions/programming-9/bash-script-return-full-path-and-filename-680368/page3.html has the following
function abspath {
if [[ -d "$1" ]]
then
pushd "$1" >/dev/null
pwd
popd >/dev/null
elif [[ -e "$1" ]]
then
pushd "$(dirname "$1")" >/dev/null
echo "$(pwd)/$(basename "$1")"
popd >/dev/null
else
echo "$1" does not exist! >&2
return 127
fi
}
which uses pushd/popd to get into a state where pwd is useful.
Simple one-liner:
function abs_path {
(cd "$(dirname '$1')" &>/dev/null && printf "%s/%s" "$PWD" "${1##*/}")
}
Usage:
function do_something {
local file=$(abs_path $1)
printf "Absolute path to %s: %s\n" "$1" "$file"
}
do_something $HOME/path/to/some\ where
I am still trying to figure out how I can get it to be completely oblivious to whether the path exists or not (so it can be used when creating files as well).
This does the trick for me on OS X: $(cd SOME_DIRECTORY 2> /dev/null && pwd -P)
It should work anywhere. The other solutions seemed too complicated.
If your OS supports it, use:
realpath -s "./some/dir"
And using it in a variable:
some_path="$(realpath -s "./some/dir")"
Which will expand your path. Tested on Ubuntu and CentOS, might not be available on yours. Some recommend readlink, but documentation for readlink says:
Note realpath(1) is the preferred command to use for canonicalization functionality.
In case people wonder why I quote my variables, it's to preserve spaces in paths. Like doing realpath some path will give you two different path results. But realpath "some path" will return one. Quoted parameters ftw :)
Thanks to NyanPasu64 for the heads up. You'll want to add -s if you don't want it to follow the symlinks.
Use readlink -f <relative-path>, e.g.
export FULLPATH=`readlink -f ./`
Maybe this is more readable and does not use a subshell and does not change the current dir:
dir_resolve() {
local dir=`dirname "$1"`
local file=`basename "$1"`
pushd "$dir" &>/dev/null || return $? # On error, return error code
echo "`pwd -P`/$file" # output full, link-resolved path with filename
popd &> /dev/null
}
on OS X you can use
stat -f "%N" YOUR_PATH
on linux you might have realpath executable. if not, the following might work (not only for links):
readlink -c YOUR_PATH
There's another method. You can use python embedding in bash script to resolve a relative path.
abs_path=$(python3 - <<END
from pathlib import Path
path = str(Path("$1").expanduser().resolve())
print(path)
END
)
self edit, I just noticed the OP said he's not looking for symlinks resolved:
"But for the functions I've written I need paths that are absolute, but do not have their symlinks resolved."
So guess this isn't so apropos to his question after all. :)
Since I've run into this many times over the years, and this time around I needed a pure bash portable version that I could use on OSX and linux, I went ahead and wrote one:
The living version lives here:
https://github.com/keen99/shell-functions/tree/master/resolve_path
but for the sake of SO, here's the current version (I feel it's well tested..but I'm open to feedback!)
Might not be difficult to make it work for plain bourne shell (sh), but I didn't try...I like $FUNCNAME too much. :)
#!/bin/bash
resolve_path() {
#I'm bash only, please!
# usage: resolve_path <a file or directory>
# follows symlinks and relative paths, returns a full real path
#
local owd="$PWD"
#echo "$FUNCNAME for $1" >&2
local opath="$1"
local npath=""
local obase=$(basename "$opath")
local odir=$(dirname "$opath")
if [[ -L "$opath" ]]
then
#it's a link.
#file or directory, we want to cd into it's dir
cd $odir
#then extract where the link points.
npath=$(readlink "$obase")
#have to -L BEFORE we -f, because -f includes -L :(
if [[ -L $npath ]]
then
#the link points to another symlink, so go follow that.
resolve_path "$npath"
#and finish out early, we're done.
return $?
#done
elif [[ -f $npath ]]
#the link points to a file.
then
#get the dir for the new file
nbase=$(basename $npath)
npath=$(dirname $npath)
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -d $npath ]]
then
#the link points to a directory.
cd "$npath"
ndir=$(pwd -P)
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition inside link!!" >&2
echo "opath [[ $opath ]]" >&2
echo "npath [[ $npath ]]" >&2
return 1
fi
else
if ! [[ -e "$opath" ]]
then
echo "$FUNCNAME: $opath: No such file or directory" >&2
return 1
#and break early
elif [[ -d "$opath" ]]
then
cd "$opath"
ndir=$(pwd -P)
retval=0
#done
elif [[ -f "$opath" ]]
then
cd $odir
ndir=$(pwd -P)
nbase=$(basename "$opath")
retval=0
#done
else
echo "$FUNCNAME: ERROR: unknown condition outside link!!" >&2
echo "opath [[ $opath ]]" >&2
return 1
fi
fi
#now assemble our output
echo -n "$ndir"
if [[ "x${nbase:=}" != "x" ]]
then
echo "/$nbase"
else
echo
fi
#now return to where we were
cd "$owd"
return $retval
}
here's a classic example, thanks to brew:
%% ls -l `which mvn`
lrwxr-xr-x 1 draistrick 502 29 Dec 17 10:50 /usr/local/bin/mvn# -> ../Cellar/maven/3.2.3/bin/mvn
use this function and it will return the -real- path:
%% cat test.sh
#!/bin/bash
. resolve_path.inc
echo
echo "relative symlinked path:"
which mvn
echo
echo "and the real path:"
resolve_path `which mvn`
%% test.sh
relative symlinked path:
/usr/local/bin/mvn
and the real path:
/usr/local/Cellar/maven/3.2.3/libexec/bin/mvn
Do you have to use bash exclusively? I needed to do this and got fed up with differences between Linux and OS X. So I used PHP for a quick and dirty solution.
#!/usr/bin/php <-- or wherever
<?php
{
if($argc!=2)
exit();
$fname=$argv[1];
if(!file_exists($fname))
exit();
echo realpath($fname)."\n";
}
?>
I know it's not a very elegant solution but it does work.