Zistenia: ACCESS(1) ACCESS(1) NAME access - determine whether a file can be accessed SYNOPSIS access -mode file DESCRIPTION Exit successfully if file can be accessed with the speci- fied mode. mode is one or more letters of rwx, where r is for readable, w is for writable, and x is for executable. The difference between access and test is that the latter looks at the permission bits, while the former checks using the access(2) system call. This makes a difference when file systems have been mounted read-only. OPTIONS access accepts the following additional options: --help Print help message and exit. --version Print version information and exit. SEE ALSO access(2) -------------------------------------------------------------------------- -r filename vrati, ci je subor readable -x filename vrati, ci je subor executable -w filename writable ------------------------------------------------------------------------- -a file True if file exists. -b file True if file exists and is a block special file. -c file True if file exists and is a character special file. -d file True if file exists and is a directory. -e file True if file exists. -f file True if file exists and is a regular file. -g file True if file exists and is set-group-id. -h file True if file exists and is a symbolic link. -k file True if file exists and its ``sticky'' bit is set. -p file True if file exists and is a named pipe (FIFO). -r file True if file exists and is readable. -s file True if file exists and has a size greater than zero. -t fd True if file descriptor fd is open and refers to a terminal. -u file True if file exists and its set-user-id bit is set. -w file True if file exists and is writable. -x file True if file exists and is executable. -O file True if file exists and is owned by the effective user id. -G file True if file exists and is owned by the effective group id. -L file True if file exists and is a symbolic link. -S file True if file exists and is a socket. -N file True if file exists and has been modified since it was last read. file1 -nt file2 True if file1 is newer (according to modification date) than file2. file1 -ot file2 True if file1 is older than file2. file1 -ef file2 True if file1 and file2 have the same device and inode numbers. -o optname True if shell option optname is enabled. See the list of options under the description of the -o option to the set builtin below. -z string True if the length of string is zero. -n string string True if the length of string is non-zero. ---------------------------------------------------------------------------- %[DIGITS | WORD] [&] . filename : [ arg... ] alias [-p] [name[=value] ... ] bg [job_spec] bind [-lpvsPVS] [-m keymap] [-f fi break [n] builtin [shell-builtin [arg ...]] case WORD in [PATTERN [| PATTERN]. cd [-PL] [dir] command [-pVv] command [arg ...] continue [n] declare [-afFrxi] [-p] name[=value dirs [-clpv] [+N] [-N] disown [-h] [-ar] [jobspec ...] echo [-neE] [arg ...] enable [-pnds] [-a] [-f filename] eval [arg ...] exec [-cl] [-a name] file [redirec exit [n] export [-nf] [name ...] or export false fc [-e ename] [-nlr] [first] [last fg [job_spec] for NAME [in WORDS ... ;] do COMMA function NAME { COMMANDS ; } or NA getopts optstring name [arg] hash [-r] [-p pathname] [name ...] help [pattern ...] history [-c] [n] or history -awrn if COMMANDS; then COMMANDS; [ elif jobs [-lnprs] [jobspec ...] or job kill [-s sigspec | -n signum | -si let arg [arg ...] local name[=value] ... logout popd [+N | -N] [-n] printf format [arguments] pushd [dir | +N | -N] [-n] pwd [-PL] read [-r] [-p prompt] [-a array] [ readonly [-anf] [name ...] or read return [n] select NAME [in WORDS ... ;] do CO set [--abefhkmnptuvxBCHP] [-o opti shift [n] shopt [-pqsu] [-o long-option] opt source filename suspend [-f] test [expr] time [-p] PIPELINE times trap [arg] [signal_spec ...] or tr true type [-apt] name [name ...] typeset [-afFrxi] [-p] name[=value ulimit [-SHacdflmnpstuv] [limit] umask [-p] [-S] [mode] unalias [-a] [name ...] unset [-f] [-v] [name ...] until COMMANDS; do COMMANDS; done variables - Some variable names an wait [n] while COMMANDS; do COMMANDS; done { COMMANDS ; } PASSWD(1) PASSWD(1) NAME passwd - change user password SYNOPSIS passwd [-f|-s] [name] passwd [-g] [-r|R] group passwd [-x max] [-n min] [-w warn] [-i inact] name passwd {-l|-u|-d|-S|-e} name DESCRIPTION passwd changes passwords for user and group accounts. A normal user may only change the password for their own account, the super user may change the password for any account. The administrator of a group may change the password for the group. passwd also changes account information, such as the full name of the user, their login shell, or password expiry dates and intervals. Password Changes The user is first prompted for their old password, if one is present. This password is then encrypted and compared against the stored password. The user has only one chance to enter the correct password. The super user is permit- ted to bypass this step so that forgotten passwords may be changed. After the password has been entered, password aging infor- mation is checked to see if the user is permitted to change their password at this time. If not, passwd refuses to change the password and exits. The user is then prompted for a replacement password. This password is tested for complexity. As a general guideline, passwords should consist of 6 to 8 characters including one or more from each of following sets: Lower case alphabetics Upper case alphabetics Digits 0 thru 9 Punctuation marks Care must be taken not to include the system default erase or kill characters. passwd will reject any password which is not suitably complex. If the password is accepted, passwd will prompt again and compare the second entry against the first. Both entries are require to match in order for the password to be changed. Group passwords When the -g option is used, the password for the named group is changed. The user must either be the super user, or a group administrator for the named group. The current group password is not prompted for. The -r option is used with the -g option to remove the current password from the named group. This allows group access to all members. The -R option is used with the -g option to restrict the named group for all users. Password expiry information The password aging information may be changed by the super user with the -x, -n, -w, and -i options. The -x option is used to set the maximum number of days a password remains valid. After max days, the password is required to be changed. The -n option is used to set the minimum number of days before a password may be changed. The user will not be permitted to change the password until min days have elapsed. The -w option is used to set the num- ber of days of warning the user will receive before their password will expire. The warning occurs warn days before the expiration, telling the user how many days until the password is set to expire. The -i option is used to dis- able an account after the password has been expired for a number of days. After a user account has had an expired password for inact days, the user may no longer sign on to the account. Account maintenance User accounts may be locked and unlocked with the -l and -u flags. The -l option disables an account by changing the password to a value which matches no possible encrypted value. The -u option re-enables an account by changing the password back to its previous value. If you wish to immediately expire an accounts password, you can use the -e option. This in affect can force a user to change their password at their next login. You can also use the -d option to delete a users password (make it empty). Use caution with this option since it can make an account not require a password at all to login, leaving your system open to intruders. The account status may be given with the -S option. The status information consists of 6 parts. The first part indicates if the user account is locked (L), has no pass- word (NP), or has a usable password (P). The second part gives the date of the last password change. The next four parts are the minimum age, maximum age, warning period, and inactivity period for the password. Hints for user passwords The security of a password depends upon the strength of the encryption algorithm and the size of the key space. The UNIX System encryption method is based on the NBS DES algorithm and is very secure. The size of the key space depends upon the randomness of the password which is selected. The -s option makes passwd call chsh to change the users shell. The -f option makes passwd call chfn to change the users gecos information. These two options are only meant for compatiblity, since the other programs can be called directly. Compromises in password security normally result from careless password selection or handling. For this reason, you should select a password which does not appear in a dictionary or which must be written down. The password should also not be a proper name, your license number, birth date, or street address. Any of these may be used as guesses to violate system security. Your password must easily remembered so that you will not be forced to write it on a piece of paper. This can be accomplished by appending two small words together and separating each with a special character or digit. For example, Pass%word. Other methods of construction involve selecting an easily remembered phrase from literature and selecting the first or last letter from each. An example of this is Ask not for whom the bell tolls. which produces An4wtbt. ----------------------------------------------------------------------- ACCESS(2) System calls ACCESS(2) NAME access - check user's permissions for a file SYNOPSIS #include int access(const char *pathname, int mode); DESCRIPTION access checks whether the process would be allowed to read, write or test for existence of the file (or other file system object) whose name is pathname. If pathname is a symbolic link permissions of the file referred to by this symbolic link are tested. mode is a mask consisting of one or more of R_OK, W_OK, X_OK and F_OK. R_OK, W_OK and X_OK request checking whether the file exists and has read, write and execute permissions, respectively. F_OK just requests checking for the exis- tence of the file. The tests depend on the permissions of the directories occurring in the path to the file, as given in pathname, and on the permissions of directories and files referred to by symbolic links encountered on the way. The check is done with the process's real uid and gid, rather than with the effective ids as is done when actu- ally attempting an operation. This is to allow set-UID programs to easily determine the invoking user's author- ity. Only access bits are checked, not the file type or con- tents. Therefore, if a directory is found to be "writable," it probably means that files can be created in the directory, and not that the directory can be written as a file. Similarly, a DOS file may be found to be "exe- cutable," but the execve(2) call will still fail. RETURN VALUE On success (all requested permissions granted), zero is returned. On error (at least one bit in mode asked for a permission that is denied, or some other error occurred), -1 is returned, and errno is set appropriately. ERRORS EACCES The requested access would be denied to the file or search permission is denied to one of the directo- ries in pathname. EROFS Write permission was requested for a file on a read-only filesystem. ------------------------------------------------------------------------- STRING(3) Linux Programmer's Manual STRING(3) NAME strcasecmp, strcat, strchr, strcmp, strcoll, strcpy, strc- spn, strdup, strfry, strlen, strncat, strncmp, strncpy, strncasecmp, strpbrk, strrchr, strsep, strspn, strstr, strtok, strxfrm, index, rindex - string operations SYNOPSIS #include int strcasecmp(const char *s1, const char *s2); char *strcat(char *dest, const char *src); char *strchr(const char *s, int c); int strcmp(const char *s1, const char *s2); int strcoll(const char *s1, const char *s2); char *strcpy(char *dest, const char *src); size_t strcspn(const char *s, const char *reject); char *strdup(const char *s); char *strfry(char *string); size_t strlen(const char *s); char *strncat(char *dest, const char *src, size_t n); int strncmp(const char *s1, const char *s2, size_t n); char *strncpy(char *dest, const char *src, size_t n); int strncasecmp(const char *s1, const char *s2, size_t n); char *strpbrk(const char *s, const char *accept); char *strrchr(const char *s, int c); char *strsep(char **stringp, const char *delim); size_t strspn(const char *s, const char *accept); char *strstr(const char *haystack, const char *needle); char *strtok(char *s, const char *delim); size_t strxfrm(char *dest, const char *src, size_t n); char *index(const char *s, int c); char *rindex(const char *s, int c); --------------------------------------------------------------------------------