This checks if a file exists:
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File $FILE exists."
else
echo "File $FILE does not exist."
fi
How do I only check if the file does not exist?
The test command (written as [ here) has a "not" logical operator, ! (exclamation mark):
if [ ! -f /tmp/foo.txt ]; then
echo "File not found!"
fi
Bash File Testing
-b filename - Block special file
-c filename - Special character file
-d directoryname - Check for directory Existence
-e filename - Check for file existence, regardless of type (node, directory, socket, etc.)
-f filename - Check for regular file existence not a directory
-G filename - Check if file exists and is owned by effective group ID
-G filename set-group-id - True if file exists and is set-group-id
-k filename - Sticky bit
-L filename - Symbolic link
-O filename - True if file exists and is owned by the effective user id
-r filename - Check if file is a readable
-S filename - Check if file is socket
-s filename - Check if file is nonzero size
-u filename - Check if file set-user-id bit is set
-w filename - Check if file is writable
-x filename - Check if file is executable
How to use:
#!/bin/bash
file=./file
if [ -e "$file" ]; then
echo "File exists"
else
echo "File does not exist"
fi
A test expression can be negated by using the ! operator
#!/bin/bash
file=./file
if [ ! -e "$file" ]; then
echo "File does not exist"
else
echo "File exists"
fi
Negate the expression inside test (for which [ is an alias) using !:
#!/bin/bash
FILE=$1
if [ ! -f "$FILE" ]
then
echo "File $FILE does not exist"
fi
The relevant man page is man test or, equivalently, man [ -- or help test or help [ for the built-in bash command.
Alternatively (less commonly used) you can negate the result of test using:
if ! [ -f "$FILE" ]
then
echo "File $FILE does not exist"
fi
That syntax is described in "man 1 bash" in sections "Pipelines" and "Compound Commands".
[[ -f $FILE ]] || printf '%s does not exist!\n' "$FILE"
Also, it's possible that the file is a broken symbolic link, or a non-regular file, like e.g. a socket, device or fifo. For example, to add a check for broken symlinks:
if [[ ! -f $FILE ]]; then
if [[ -L $FILE ]]; then
printf '%s is a broken symlink!\n' "$FILE"
else
printf '%s does not exist!\n' "$FILE"
fi
fi
It's worth mentioning that if you need to execute a single command you can abbreviate
if [ ! -f "$file" ]; then
echo "$file"
fi
to
test -f "$file" || echo "$file"
or
[ -f "$file" ] || echo "$file"
I prefer to do the following one-liner, in POSIX shell compatible format:
$ [ -f "/$DIR/$FILE" ] || echo "$FILE NOT FOUND"
$ [ -f "/$DIR/$FILE" ] && echo "$FILE FOUND"
For a couple of commands, like I would do in a script:
$ [ -f "/$DIR/$FILE" ] || { echo "$FILE NOT FOUND" ; exit 1 ;}
Once I started doing this, I rarely use the fully typed syntax anymore!!
To test file existence, the parameter can be any one of the following:
-e: Returns true if file exists (regular file, directory, or symlink)
-f: Returns true if file exists and is a regular file
-d: Returns true if file exists and is a directory
-h: Returns true if file exists and is a symlink
All the tests below apply to regular files, directories, and symlinks:
-r: Returns true if file exists and is readable
-w: Returns true if file exists and is writable
-x: Returns true if file exists and is executable
-s: Returns true if file exists and has a size > 0
Example script:
#!/bin/bash
FILE=$1
if [ -f "$FILE" ]; then
echo "File $FILE exists"
else
echo "File $FILE does not exist"
fi
You can do this:
[[ ! -f "$FILE" ]] && echo "File doesn't exist"
or
if [[ ! -f "$FILE" ]]; then
echo "File doesn't exist"
fi
If you want to check for file and folder both, then use -e option instead of -f. -e returns true for regular files, directories, socket, character special files, block special files etc.
You should be careful about running test for an unquoted variable, because it might produce unexpected results:
$ [ -f ]
$ echo $?
0
$ [ -f "" ]
$ echo $?
1
The recommendation is usually to have the tested variable surrounded by double quotation marks:
#!/bin/sh
FILE=$1
if [ ! -f "$FILE" ]
then
echo "File $FILE does not exist."
fi
In
[ -f "$file" ]
the [ command does a stat() (not lstat()) system call on the path stored in $file and returns true if that system call succeeds and the type of the file as returned by stat() is "regular".
So if [ -f "$file" ] returns true, you can tell the file does exist and is a regular file or a symlink eventually resolving to a regular file (or at least it was at the time of the stat()).
However if it returns false (or if [ ! -f "$file" ] or ! [ -f "$file" ] return true), there are many different possibilities:
the file doesn't exist
the file exists but is not a regular file (could be a device, fifo, directory, socket...)
the file exists but you don't have search permission to the parent directory
the file exists but that path to access it is too long
the file is a symlink to a regular file, but you don't have search permission to some of the directories involved in the resolution of the symlink.
... any other reason why the stat() system call may fail.
In short, it should be:
if [ -f "$file" ]; then
printf '"%s" is a path to a regular file or symlink to regular file\n' "$file"
elif [ -e "$file" ]; then
printf '"%s" exists but is not a regular file\n' "$file"
elif [ -L "$file" ]; then
printf '"%s" exists, is a symlink but I cannot tell if it eventually resolves to an actual file, regular or not\n' "$file"
else
printf 'I cannot tell if "%s" exists, let alone whether it is a regular file or not\n' "$file"
fi
To know for sure that the file doesn't exist, we'd need the stat() system call to return with an error code of ENOENT (ENOTDIR tells us one of the path components is not a directory is another case where we can tell the file doesn't exist by that path). Unfortunately the [ command doesn't let us know that. It will return false whether the error code is ENOENT, EACCESS (permission denied), ENAMETOOLONG or anything else.
The [ -e "$file" ] test can also be done with ls -Ld -- "$file" > /dev/null. In that case, ls will tell you why the stat() failed, though the information can't easily be used programmatically:
$ file=/var/spool/cron/crontabs/root
$ if [ ! -e "$file" ]; then echo does not exist; fi
does not exist
$ if ! ls -Ld -- "$file" > /dev/null; then echo stat failed; fi
ls: cannot access '/var/spool/cron/crontabs/root': Permission denied
stat failed
At least ls tells me it's not because the file doesn't exist that it fails. It's because it can't tell whether the file exists or not. The [ command just ignored the problem.
With the zsh shell, you can query the error code with the $ERRNO special variable after the failing [ command, and decode that number using the $errnos special array in the zsh/system module:
zmodload zsh/system
ERRNO=0
if [ ! -f "$file" ]; then
err=$ERRNO
case $errnos[err] in
("") echo exists, not a regular file;;
(ENOENT|ENOTDIR)
if [ -L "$file" ]; then
echo broken link
else
echo does not exist
fi;;
(*) syserror -p "can't tell: " "$err"
esac
fi
(beware the $errnos support was broken with some versions of zsh when built with recent versions of gcc).
There are three distinct ways to do this:
Negate the exit status with bash (no other answer has said this):
if ! [ -e "$file" ]; then
echo "file does not exist"
fi
Or:
! [ -e "$file" ] && echo "file does not exist"
Negate the test inside the test command [ (that is the way most answers before have presented):
if [ ! -e "$file" ]; then
echo "file does not exist"
fi
Or:
[ ! -e "$file" ] && echo "file does not exist"
Act on the result of the test being negative (|| instead of &&):
Only:
[ -e "$file" ] || echo "file does not exist"
This looks silly (IMO), don't use it unless your code has to be portable to the Bourne shell (like the /bin/sh of Solaris 10 or earlier) that lacked the pipeline negation operator (!):
if [ -e "$file" ]; then
:
else
echo "file does not exist"
fi
envfile=.env
if [ ! -f "$envfile" ]
then
echo "$envfile does not exist"
exit 1
fi
To reverse a test, use "!".
That is equivalent to the "not" logical operator in other languages. Try this:
if [ ! -f /tmp/foo.txt ];
then
echo "File not found!"
fi
Or written in a slightly different way:
if [ ! -f /tmp/foo.txt ]
then echo "File not found!"
fi
Or you could use:
if ! [ -f /tmp/foo.txt ]
then echo "File not found!"
fi
Or, presing all together:
if ! [ -f /tmp/foo.txt ]; then echo "File not found!"; fi
Which may be written (using then "and" operator: &&) as:
[ ! -f /tmp/foo.txt ] && echo "File not found!"
Which looks shorter like this:
[ -f /tmp/foo.txt ] || echo "File not found!"
The test thing may count too. It worked for me (based on Bash Shell: Check File Exists or Not):
test -e FILENAME && echo "File exists" || echo "File doesn't exist"
This code also working .
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File '$FILE' Exists"
else
echo "The File '$FILE' Does Not Exist"
fi
The simplest way
FILE=$1
[ ! -e "${FILE}" ] && echo "does not exist" || echo "exists"
This shell script also works for finding a file in a directory:
echo "enter file"
read -r a
if [ -s /home/trainee02/"$a" ]
then
echo "yes. file is there."
else
echo "sorry. file is not there."
fi
sometimes it may be handy to use && and || operators.
Like in (if you have command "test"):
test -b $FILE && echo File not there!
or
test -b $FILE || echo File there!
If you want to use test instead of [], then you can use ! to get the negation:
if ! test "$FILE"; then
echo "does not exist"
fi
You can also group multiple commands in the one liner
[ -f "filename" ] || ( echo test1 && echo test2 && echo test3 )
or
[ -f "filename" ] || { echo test1 && echo test2 && echo test3 ;}
If filename doesn't exit, the output will be
test1
test2
test3
Note: ( ... ) runs in a subshell, { ... ;} runs in the same shell.
My code is:
-cname)
changeName="{2}"
if [ -z $changeName ]; then
echo -en "Which note name do you want to change?"
read -r $changeName
echo "What would you like to change the name to?"
read -r changeNewName
if ! [ -z "${3}" ]; then
echo "The name has to have no spaces."
exit 1
fi
if [ -f /usr/share/cnote/notes/$changeNewName ]; then
echo "That note name is already used. Please choose a new one."
exit 1
fi
cp "/usr/share/cnote/notes/${changeName}" "/usr/share/cnote/notes/${changeNewName}"
;;
If I remove this part of my case statement it works again but with that part I get that error:
root#minibian:~/cnote# ./cnote -cname
./cnote: line 73: syntax error near unexpected token ;;'
./cnote: line 73: ;;'
Your first if block is not closed. and you should not put the $ symbol ahead of changeName. So the first part must be
if [ -z $changeName ]; then
echo -en "Which note name do you want to change?"
read -r changeName
echo "What would you like to change the name to?"
read -r changeNewName
fi
This code is that I want to give two directory and this code will look if these two directory contains two files that contains the same information, and asks me which file I want to delete .
I have written this code but I don't know how to write the code that will delete the file , please help
#!bin/bash
echo "give the first directory"
read firstdir
echo "give the second directory"
read seconddir
for i in ` ls $firstdir`
do
echo $i
t= `md5sum $firstdir/$i`
s= `md5sum $seconddir/$i`
if [ "$t" ! = "$s" ]
then
echo " of which directory will be eliminated? $i"
read direct
( here I want the code to delete the directory ex : delete direct/i )
fi
done
Replace:
echo " of which directory will be eliminated? $i"
read direct
( here I want the code to delete the directory ex : delete direct/i )
With:
echo "of which directory will be eliminated? $i:
1)$firstdir
2)$seconddir
"
read -p "(1/2)" direct
case $direct in
1)
rm -v $firstdir/$i
;;
2)
rm -v $seconddir/$i
;;
*)
echo "ERROR: bad value, 1 or 2 expected!" ; exit 1
esac
Ok, try this. I just made my own solution based on your requirements. I hope you like it. Thanks
#!/bin/bash
# check for a valid first directory
while true
do
echo "Please, enter the first directory"
read FIRST_DIR
if [ -d $FIRST_DIR ]; then
break
else
echo "Invalid directory"
fi
done
# check for a valid second directory
while true
do
echo "Please, give the second directory"
read SECOND_DIR
if [ -d $SECOND_DIR ]; then
break
else
echo "Invalid directory"
fi
done
for FILE in `ls $FIRST_DIR`
do
# make sure that only files will be avaluated
if [ -f $FILE ]; then
echo $SECOND_DIR/$FILE
# check if the file exist in the second directory
if [ -f $SECOND_DIR/$FILE ]; then
# compare the two files
output=`diff -c $FIRST_DIR/$FILE $SECOND_DIR/$FILE`
if [ ! $output ]; then
echo "Which file do you want to delete?
1)$FIRST_DIR/$FILE
2)$SECOND_DIR/$FILE
"
# read a choice
read -p "(1/2)" choice
# delete the chosen file
case $choice in
1)
rm -v $FIRST_DIR/$FILE
;;
2)
rm -v $SECOND_DIR/$FILE
;;
*)
echo "ERROR invalid choice!"
esac
fi
else
echo "There are no equal files in the two directories."
exit 1
fi
else
echo "There are no files to be evaluated."
fi
done
My Code:
#!/bin/bash
rm screenlog.0
screen -X stuff 'X21'$(printf \\r)
while :
do
grep -i "T" $screenlog.0
if [ $? -eq 0 ];
then
FILE=/etc/passwd
VAR=`head -n 1 $FILE`
echo $VAR
rm screenlog.0
break
done
This script is to delete the file "screenlog.0" send a command (X21) to an screen interface.
Thats the first part and it works.
The second Part is the Problem:
That should test the content of "screenlog.0", is there an something with a "T" inside save the contant into a variable.
The error:
line 11: syntax error near unexpected token `done'
line 11: `done'
To the "screen": Its an screen of an usb device that recive radio messages like this:
T350B00A66E2
H34D04DE4254
The script have to scan for the incomming messages with "T" at the beginning (The first letter is a Type field behind this a hex code.
Some ideas to correct or other solutions?
I corrected my code a bit:
#!/bin/bash
>screenlog.0
screen -X stuff 'X21'$(printf \\r)
while :
do
sleep 2
grep -i "T" $screenlog.0
if [ $? -eq 0 ];
then
screenlog.0=/etc/passwd
VAR=`head -n 1 $screenlog.0`
echo $VAR
break
fi
done
The new error is:
grep: .0: No such file or directory
All 5 seconds....
The file screenlog.0 exist .. :(
oh...you missed fi in your script :). Like syntax as follows if [ condition ];then #dosomething fi
For your script
if [ $? -eq 0 ];then
FILE=/etc/passwd
VAR=`head -n 1 $FILE`
echo $VAR
rm screenlog.0
break
fi
I have a bash script which I would like to handle spaces. I know there a ton of questions on here about this, but I was unable to resolve my problem.
According to what I've read, the following should work. The space in
../tool_profile/OS\ Firmware/updater is being escaped. In the script, the $2 variable is being enclosed in quotes when being assigned to DEST.
If I pass this path in to ls enclosed in quotes or with escaped spaces on the command line, it works.
example script command:
./make_initramfs.sh initramfs_root/ ../tool_profile/OS\ Firmware/updater/ initramfs
error from ls in script:
ls: cannot access ../tool_profile/OS Firmware/updater/: No such file or directory
make_initramfs.sh:
#!/bin/bash
if [ $# -ne 3 ]; then
echo "Usage: `basename $0` <root> <dest> <archive_name>"
exit 1
fi
ROOT=$1
DEST="$2"
NAME=$3
echo "[$DEST]"
# cd and hide output
cd $ROOT 2&>/dev/null
if [ $? -eq 1 ]; then
echo "invalid root: $ROOT"
exit 1
fi
ls "$2" # doesn't work
ls "$DEST" # doesn't work
# check for 'ls' errors
#if [ $? -eq 1 ]; then
# echo "invalid dest: $DEST"
# exit 1
#fi
#sudo find . | sudo cpio -H newc -o | gzip --best > "$DEST"/"$NAME"
Thank you for any clues to what I am doing wrong! ^_^
Okay... so right as I submitted this I realized what I was doing wrong.
I was passing two relative paths in and changing to the first one before verifying the second one. So once I changed directory, the second relative path was no longer valid. I will post an updated script once I get it finished.
Edit: I finished my script. See below.
Edit2: I updated this based on everyone's comments. Thanks everyone!
make_initramfs.sh:
#!/bin/bash
if (( $# != 2 )); then
echo "Usage: `basename $0` <root> <dest>"
exit 1
fi
root="$1"
archive="${2##*/}"
dest="$PWD/${2%/*}"
# cd and hide errors
cd "$root" &>/dev/null
if (( $? != 0 )); then
echo "invalid path: $root"
exit 1
fi
if [ ! -d "$dest" ]; then
echo "invalid path: $dest"
exit 1
fi
if [ "$archive" = "" ]; then
echo "no archive file specified"
exit 1
fi
if [ `whoami` != root ]; then
echo "please run this script as root or using sudo"
exit 1
fi
find . | cpio -H newc -o | gzip --best > "$dest"/"$archive"