If statements in Linux terminal Post: 302861175

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Homework and Emergencies Homework & Coursework Questions If statements in Linux terminal Post 302861175 by sea on Tuesday 8th of October 2013 09:52:43 AM

10-08-2013

Registered User

First time i see constantly used the ( for if statements, i'm used to [..

Regard 'if statements'...
[[ condition ]] && echo succeeded || echo failed

Example:
[[ -z $XDG_DESKTOP_DIR ]] && echo "Your desktop is: $XDG_DESKTOP_DIR" || echo "$HOME/.config/user-dirs.dirs not loaded yet."

Which is the same as: (note the '\', that tells the line isnt dont yet, there must be no trailing spaces!)

Code:

[[ -z $XDG_DESKTOP_DIR ]] && \
    echo "Your desktop is: $XDG_DESKTOP_DIR" || \
    echo "$HOME/.config/user-dirs.dirs not loaded yet."

Which i prefer for 'short code' like setting a variable.

The && is appending the following command if previous command returns 0/true.
The || indicates what is done if the previous condition/command failed.

Examples:

Code:

[[ ! 0 -eq $UID ]] && echo "You're not root, and we abort" && exit
[[ 0 -eq $UID ]] || echo "You're not root, but we continue anyway"
[[ 0 -eq $UID ]] && echo "Must not be root!" && exit || echo "You may pass $USER"

hth

Last edited by sea; 10-08-2013 at 11:03 AM.. Reason: uh.. wasnt asked.. but since we're on it..

sea

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mkdtemp

MKDTEMP(3)						     Linux Programmer's Manual							MKDTEMP(3)

NAME

       mkdtemp - create a unique temporary directory

SYNOPSIS

       #include <stdlib.h>

       char *mkdtemp(char *template);

DESCRIPTION

       The mkdtemp() function generates a uniquely-named temporary directory from template. The last six characters of template must be XXXXXX and
       these are replaced with a string that makes the directory name unique. The directory is then created with permissions 0700.  Since it  will
       be modified, template must not be a string constant, but should be declared as a character array.

RETURN VALUE

       The mkdtemp() function returns a pointer to the modified template string on success, and NULL on failure, in which case errno is set appro-
       priately.

ERRORS

       EINVAL The last six characters of template were not XXXXXX.  Now template is unchanged.

       Also see mkdir(2) for other possible values for errno.

CONFORMING TO

       Introduced in OpenBSD 2.2.  Available since glibc 2.1.91.

SEE ALSO

       mkdir(2), mkstemp(3), mktemp(3), tmpnam(3), tempnam(3), tmpfile(3)

GNU
								    2001-10-07								MKDTEMP(3)