To check if a directory exists in a shell script, you can use the following:
if [ -d "$DIRECTORY" ]; then
# Control will enter here if $DIRECTORY exists.
fi
Or to check if a directory doesn't exist:
if [ ! -d "$DIRECTORY" ]; then
# Control will enter here if $DIRECTORY doesn't exist.
fi
However, as Jon Ericson points out, subsequent commands may not work as intended if you do not take into account that a symbolic link to a directory will also pass this check.
E.g. running this:
ln -s "$ACTUAL_DIR" "$SYMLINK"
if [ -d "$SYMLINK" ]; then
rmdir "$SYMLINK"
fi
Will produce the error message:
rmdir: failed to remove `symlink': Not a directory
So symbolic links may have to be treated differently, if subsequent commands expect directories:
if [ -d "$LINK_OR_DIR" ]; then
if [ -L "$LINK_OR_DIR" ]; then
# It is a symlink!
# Symbolic link specific commands go here.
rm "$LINK_OR_DIR"
else
# It's a directory!
# Directory command goes here.
rmdir "$LINK_OR_DIR"
fi
fi
Take particular note of the double-quotes used to wrap the variables. The reason for this is explained by 8jean in another answer.
If the variables contain spaces or other unusual characters it will probably cause the script to fail.
A lot of the answers here helped point me in the right direction, however none were suitable for me, so I am posting my solution.
I have Windows 7, which comes with PowerShell built-in. Here is the script I used to find/replace all instances of text in a file:
powershell -Command "(gc myFile.txt) -replace 'foo', 'bar' | Out-File -encoding ASCII myFile.txt"
To explain it:
powershell
starts up powershell.exe, which is included in Windows 7
-Command "... "
is a command line arg for powershell.exe containing the command to run
(gc myFile.txt)
reads the content of myFile.txt
(gc
is short for the Get-Content
command)
-replace 'foo', 'bar'
simply runs the replace command to replace foo
with bar
| Out-File myFile.txt
pipes the output to the file myFile.txt
-encoding ASCII
prevents transcribing the output file to unicode, as the comments point out
Powershell.exe should be part of your PATH statement already, but if not you can add it. The location of it on my machine is C:\WINDOWS\system32\WindowsPowerShell\v1.0
Update
Apparently modern windows systems have PowerShell built in allowing you to access this directly using
(Get-Content myFile.txt) -replace 'foo', 'bar' | Out-File -encoding ASCII myFile.txt
Best Answer
Also worth mentioning:
tac
(the, ahem, reverse ofcat
). Part of coreutils.Flipping one file into another