i have the following csh shell script thats giving me errors and I'm not quite sure why. it essentially says that ls and cp commands are not found
#!/bin/csh
clear
set path="~/SCRAT_SIMs/V6.0/bin/linux/"
echo "Pushing files to: $path"
ls packages/
cp -r packages/acte_asym $path
cp -r packages/acte_hq/ $path
when i get rid of the set path then it seems to work. any ideas?
In csh and tcsh, the $path shell variable and the $PATH environment variable are tied together. $PATH (which applies to everything, not just the shell) is a list of directory names separated by : characters. $path is a csh array variable that mirrors the contents of $PATH.
In your case, you just need to pick a different variable name.
If you actually want to manipulate your execution path, you should usually keep the existing contents of $path and add new directories to the beginning or to the end. For example:
set path = ( ~/bin $path:q )
The :q suffix avoids problems if some directory in $PATH has funny characters like spaces. Note: Don't use double quotes here:
set path = ( ~/bin "$path" )
That will expand the entire contents of your $path to a single string with embedded spaces; $path:q keeps it as an array.
Obligatory link. (I used to write csh scripts myself, but I've found that sh and bash are much better for programming, though tcsh still has a few advantages for interactive use.)
Related
Question: Is the environment variable PWD always defined under Linux independent of the command shell (neglecting non-command shells)? In other words, will a command like "ls $PWD" always run?
Posix compliant shells will set this environment variable. Look for PWD in http://pubs.opengroup.org/onlinepubs/009604599/utilities/cd.html
PWD
This variable shall be set as specified in the DESCRIPTION. If an application sets or unsets the value of PWD , the behavior of cd is
unspecified.
or section 2.5.3 "Shell variables" in http://pubs.opengroup.org/onlinepubs/009604599/utilities/xcu_chap02.html
Variables shall be initialized from the environment... If a variable
is initialized from the environment, it shall be marked for export
immediately
PWD
Set by the shell to be an absolute pathname of the current working directory,
Is the environment variable PWD always defined under Linux independent of the command shell?
No, and I don't see why this could be the case, because the PWD variable is automatically updated (at shell initialization and) after using the cd command, which is precisely a shell builtin.
Relevant documentation about PWD can be found e.g. in:
the list of Bash variables detailed in the Bash reference manual,
the "Pwd" article in Wikipedia,
or the documentation of cd in the POSIX Standard
Below is a sample Bash session to exemplify the link between PWD and cd:
/$ echo "$SHELL"
/bin/bash
/$ echo "$PWD"
/
/$ cd usr/bin/
/usr/bin$ echo "$PWD"
/usr/bin
In other words, will a command like ls $PWD always run?
Actually, the $PWD syntax corresponds to a shell parameter expansion, so ls $PWD couldn't be properly evaluated without a shell.
A remark in passing: it is strongly recommended to double-quote your shell variables, writing thereby ls "$PWD" in this case, to avoid troubles if the variable contains spaces or other special characters.
I'm unable to use ls, bash.. any popular commands that are critical after changing the path.
I'm unsure what it was before (because I can't do vi command either).
I ran the first command, and realized the first one had a typo - not PATH, but I've typed PATh.
So I immediately ran the next one:
export PATH="/usr/local/bin:$PATh"
export PATH="/usr/local/bin:$PATH"
Then vi, ls, bash commands started to not work.
I did echo $PATH to see the PATH.
usr/local/bin:/usr/local/bin:/usr/local/bin:/usr/local/bin:
This is what I got. Any help is appreciated.
You should be able to source /etc/profile to reset your PATH variable, though it may step on a few other variables you've configured along the way. You could also just grep for the appropriate line from that to set PATH and redo that in your current environment
Also, you can always specify the full path to an executable you need in the interim. For example, if you wanted to use grep with the PATH in its current state you could use /bin/grep (or perhaps /usr/bin/grep depending your system)
1 > Try to load default .profile script
$ /bin/bash ./.profile
2 > Just Logout from current session
and Re-login it.
It appears you have "broken" your bash shell ~/.bash_profile script, because of the PATh typo. (The question explicitly states bash, so I'm answering in that context.)
Since the PATH is "broken", you will need to access your editor by using its fully qualified path.
/usr/bin/vi ~/.bash_profile
That should allow you to fix the PATh to be PATH.
If you find that you need to edit your PATH environment variable a lot, this little bash function can be helpful.
vipath() {
local tmpfile=$(mktemp /tmp/vipath-edit.XXXXXX)
echo "$PATH" | tr ':' '\n' > "$tmpfile"
vi "$tmpfile" && PATH=$(paste -s -d ':' "$tmpfile")
rm "$tmpfile"
}
Note: there are better ways to ensure the $tmpfile gets deleted that I did not use in this snippet. And on a multiuser system, there are better ways to make sure the temporary file is not located in a shared location.
If you want to add a directory location to your PATH, without adding duplicate locations, this little bash function can be helpful to prepend a directory location.
pathadd() {
if [ -d "$1" ] && [[ ! ":$PATH:" =~ ":$1:" ]]
then
PATH="$1:$PATH"
fi
}
I had the same in RHEL8, I did an export PATH for a certain directory and then no command worked anymore. I performed a faulty export PATH command probably.
I got messages like this:
>$ yum
bash: yum: command not found...
Install package 'yum' to provide command 'yum'? [N/y] n
Luckily I had some other similar systems where I could get the path from, so I did:
export PATH=/home/USER/.local/bin:/home/USER/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbine
Change USER to your own.
To make it permanent: add to $HOME/.bashrc with:
export PATH=$PATH:<YOUR PATH HERE>
When you do export PATH="/usr/local/bin:$PATH" you are saying, set PATH to /usr/local/bin: plus whatever was in the PATH variable before. This essentially concatenates the string "/usr/local/bin:" with the old path. That is why your PATH repeats so much, you must have run that command a few times.
Try running this: export PATH="/usr/local/bin".
I have a few questions on this $PATH in Linux.
I know it tells the shell which directories to search for executable files, so:
What does it mean an environmental variable?
How to change its path? and is it recommended to change it?
IF i change it what are the consequences?
To get your path current $PATH variable type in:
echo $PATH
It tells your shell where to look for binaries.
Yes, you can change it - for example add to the $PATH folder with your custom scripts.
So: if your scripts are in /usr/local/myscripts to execute them you will have to type in a full path to the script: /usr/local/myscripts/myscript.sh
After changing your $PATH variable you can just type in myscript.sh to execute script.
Here is an example of $PATH from RHEL:
/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/home/user/bin
To change your $PATH you have to either edit ~/.profile (or ~/.bash_profile) for user or global $PATH setting in /etc/profile.
One of the consequences of having inaccurate $PATH variables is that shell will not be able to find and execute programs without a full $PATH.
Firstly, you are correct in your statement of what $PATH does. If you were to break it somehow (as per your third point), you will have to manually type in /usr/bin/xyz if you want to run a program in /usr/bin from the terminal. Depending on how individual programs work, this might break some programs that invoke other ones, as they will expect to just be able to run ls or something.
So if you were to play around with $PATH, I would suggest saving it somewhere first. Use the command line instruction
echo $PATH > someRandomFile.txt
to save it in someRandomFile.txt
You can change $PATH using the export command. So
export PATH=someNewPath
HOWEVER, this will completely replace $PATH with someNewPath. Since items in path are separated by a ":", you can add items to it (best not to remove, see above) by executing
export PATH=$PATH:newPath
The fact that it is an environmental variable means that programs can find out its value, ie it is something that is set about the environment that the program is running in. Other environmental variables include things like the current directory and the address of the current proxy.
this is simple and i do like this way.
Open the linux bash shell and print the environment variables:
printenv
I copy "PATH" variable to a text editor and edit as I want. Then update the PATH like this
export PATH= /variable dir list/
It Works.
or if you want to add an single variable use this command.
export PATH = $PATH:/variable_dir_path/
This will extends the PATH with your new directory path.
I need some help understanding following shell script line,
apphome = "`cd \`dirname $0\` && pwd && cd - >/dev/null`"
All I understand is, this is creating a variable called apphome.
This is not a valid shell code.
The shell don't allow spaces around =
For the rest, while this seems broken, it try to cd to the dir of the script itself, display the current dir & finally cd back to the latest cd place redirecting his standard output STDOUT to the /dev/null trash-bin (that's makes not any sense, cd display only on standard error STDERR when it fails, never on STDOUT)
If you want to do this in a proper a simple way :
apphome="$(dirname $0)"
That's all you need.
NOTE
The backquote
`
is used in the old-style command substitution, e.g.
foo=`command`
The
foo=$(command)
syntax is recommended instead. Backslash handling inside $() is less surprising, and $() is easier to nest. See http://mywiki.wooledge.org/BashFAQ/082
It seems to assign a command to the "apphome" variable. This command can be executed later.
dirname returns a directory portion of a file name. $0 is the name of the script this line contains (if I am not mistaken).
Now, executing dirname <name> will return a directory, and cd will use the value.
So, what it would do is execute three command in the row assuming that each one of them succeeds. The commands are:
cd `dirname [name of the script]`
pwd
cd -
First command will change directory to the directory containing your script; second will print current directory; third will take yo back to the original directory. Output of the third command will not be printed out.
In summary, it will print out a name of a directory containing the script that contains the line in question.
At least, this is how I understand it.
I have read other threads enter link description herethat discuss .bat to L/unix conversions, but none has been satisfactory. I have also tried a lot of hack type approach in writing my own scripts.
I have the following example.bat script that is representative of the kind of script I want to run on unix.
Code:
echo "Example.bat"
perl script1 param.in newParam.in
perl script2 newParam.in stuff.D2D stuff.D2C
program.exe stuff.D2C
perl script3 stuff.DIS results.out
My problem is I don't know how to handle the perl and program.exe in the unix bash shell. I have tried putting them in a system(), but that did not work. Can someone please help me?
Thank you!
Provided that you have an executable file named program.exe somewhere in your $PATH (which you well might — Unix executables don't have to end in .exe, but nothing says they can't), the code you've pasted is a valid shell script. If you save it in a file named, say, example.bat, you can run it by typing
sh example.bat
into the shell prompt.
Of course, Unix shell scripts are usually given the suffix .sh — or no suffix at all — rather than .bat. Also, if you want your script to be executable directly, by typing just
example.sh
rather than sh example.sh, you need to do three things:
Start the script with a "shebang" line: a line that begins with #! and the full path to the shell interpreter you want to use to run it (e.g. /bin/sh for the basic Bourne shell), like this:
#!/bin/sh
echo "This is a shell script."
# ... more commands here ...
Mark your script as executable using the chmod command, e.g.
chmod a+rx example.sh
Put your script somewhere along your $PATH. On Unix, the default path will not normally contain the current directory ., so you can't execute programs from the current directory just by typing their name. You can, however, run them by specifying an explicit path, e.g.
./example.sh # runs example.sh from the current directory
To find out what your $PATH is, just type echo $PATH into the shell.