I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3
Related
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3
I was trying to write a Bash script that uses an if statement.
if[$CHOICE -eq 1];
The script was giving me errors until I gave a space before and after [ and before ] as shown below:
if [ $CHOICE -eq 1 ];
My question here is, why is the space around the square brackets so important in Bash?
Once you grasp that [ is a command, a whole lot becomes clearer!
[ is another way to spell "test".
help [
However while they do exactly the same, test turns out to have a more detailed help page. Check
help test
...for more information.
Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.
From another question:
A bit of history: this is because '[' was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn't surround the '[' with space, the shell would be searching $PATH for a different filename (and not find it) . – Andrew Medico Jun 24 '09 at 1:13
[ is a command and $CHOICE should be an argument, but by doing [$CHOICE (without any space between [ and $CHOICE) you are trying to run a command named [$CHOICE. The syntax for command is:
command arguments separated with space
[ is a test command. So it requires space.
It's worth noting that [ is also used in glob matching, which can get you into trouble.
$ echo [12345]
[12345]
$ echo oops >3
$ echo [12345]
3