Shell Programming and Scripting

Thank you for the basic explanation. I know well about the the splitting at spaces for unquoted variables, but thought that single quoting stops this.

Even single quoting won't make it work

Code:

#!/bin/bash -xv
CMD_LINE1='/root/Desktop/build_cm10/android_cm-10.1/system/out/host/linux-x86/bin/mkbootfs /root/Desktop/build_cm10/android_cm-10.1/system/out/target/product/n7100/recovery/root > /root/Desktop/build_cm10/android_cm-10.1/system/out/target/product/n7100/ramdisk-recovery.cpio'
$CMD_LINE1

Now, understanding that be it quoted or unquoted, every segment is passed as an argument makes things clear and evident

Thank you

Single-quoting a > will not let the shell parse it later. The quotes cease to exist when the string is stored, they only tell the shell what to do with a string right then, they don't change the meaning later. Using single quotes versus double quotes tells the shell whether to attempt anything like substituting variables right now and no other time.

Be it single or double quoted, if you force a string to contain actual quote, pipe, redirection, backtick, or dollar-sign characters, the shell will understand them to be literal characters, not anything with meaning.

In other words, storing shell statements inside strings continues to be a poor idea no matter how you cut it. There is not a mysterious "right way" to do this that we are hiding from you. If you explained your intent we could probably show you a better way to accomplish the result you want, but it would be done in a completely different manner.

Thank you
It is ok, I got it.

I never did such a thing. Was debugging quickly my script and wanted to test the whole line without a second thought. Once it failed, I did not know that the shell will always understand this as literal characters. Now it is really clear.

This is the portion I wanted to achieve since you asked:

Code:

DEVICE_ID=$1
OUT_DIR="/output/path"

# correct way to run my command:
"$OUT_DIR"/utils/mkbootfs "$OUT_DIR"/"$DEVICE_ID"/ramdisk > "$OUT_DIR"/"$DEVICE_ID"/recovery-image.cpio

If you have another opinion about it, you are welcome

I have an opinion.

Do not put double quotes around the variables, because:

1) Not needed. Makes it harder to read.
2) Nobody else writes it that way.
3) Confusing to others. They waste time trying to figure out why.

Compare:

Code:

"$OUT_DIR"/utils/mkbootfs "$OUT_DIR"/"$DEVICE_ID"/ramdisk > "$OUT_DIR"/"$DEVICE_ID"/recovery-image.cpio

Code:

$OUT_DIR/utils/mkbootfs $OUT_DIR/$DEVICE_ID/ramdisk > $OUT_DIR/$DEVICE_ID/recovery-image.cpio

yes, just a habit to limit errors if spaces under some functions
Thank you

You're right. I never put spaces in file names, instead using underscore or dash instead, because using spaces introduces little complexities like this. But you're right to use those double quotes if any chance of those spaces in the names.

Yes, mainly to run commands, using quotes is important in my opinion
To assign variables, it can be optional in some cases