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coherent
ksh Command ksh
The Korn shell
kksshh _t_o_k_e_n ...
The COHERENT system offers two command interpreters: sshh, the
Bourne shell; and kksshh, the Korn shell. sshh is the default
COHERENT command interpreter. The shell tutorial included in
this manual describes the Bourne shell in detail.
This article describes kksshh, the Korn shell. kksshh is a superset of
the Bourne shell, and contains many features that you may well
find useful. These include MicroEMACS-style editing of command
lines; command hashing; a full-featured aliasing feature; and a
job-control facility.
***** Invoking ksh *****
To invoke kksshh from within the Bourne shell, simply type kksshh at
the command-line prompt. To use kksshh as your default shell,
instead of sshh, append the command /uussrr/bbiinn/kksshh to the end of your
entry in the file /eettcc/ppaasssswwdd. (See the Lexicon entry for ppaasssswwdd
for more information on this file.)
You can invoke kksshh with one or more built-in options; these are
described below.
***** Commands *****
A _c_o_m_m_a_n_d consists of one or more _t_o_k_e_n_s. A _t_o_k_e_n is a string of
text characters (i.e., one or more alphabetic characters,
punctuation marks, and numerals) delineated by spaces, tabs, or
newlines.
A _s_i_m_p_l_e _c_o_m_m_a_n_d consists of the command's name, followed by zero
or more tokens that represent arguments to the command, names of
files, or shell operators. A _c_o_m_p_l_e_x _c_o_m_m_a_n_d will use shell
constructs to execute one or more commands conditionally. In
effect, a complex command is a mini-program that is written in
the shell's programming language and interpreted by kksshh.
***** Shell Operators *****
The shell includes a number of operators that form pipes,
redirect input and output to commands, and let you define
conditions under which commands are executed.
_c_o_m_m_a_n_d | _c_o_m_m_a_n_d
The _p_i_p_e operator: let the output of one command serve as
the input to a second. You can combine commands with `|' to
form _p_i_p_e_l_i_n_e_s. A pipeline passes the standard output of the
first (leftmost) command to the standard input of the second
command. For example, in the pipeline
sort customers | uniq | more
COHERENT Lexicon Page 1
ksh Command ksh
kksshh invokes ssoorrtt to sort the contents of file ccuussttoommeerrss. It
pipes the output of ssoorrtt to the command uunniiqq, which outputs
one unique copy of the text that is input into it. kksshh then
pipes the output of uunniiqq to the command mmoorree, which displays
it on your terminal one screenful at a time. Note that
under COHERENT, unlike MS-DOS, pipes are executed
concurrently: that is, ssoorrtt does not have to finish its work
before uunniiqq and mmoorree can begin to receive input and get to
work.
_c_o_m_m_a_n_d ; _c_o_m_m_a_n_d
Execute commands on a command line sequentially. The
command to the left of the `;' executes to completion; then
the command to the right of it executes. For example, in
the command line
a | b ; c | d
first execute the pipeline aa | bb then, when aa and bb
complete, execute the pipeline cc | dd.
_c_o_m_m_a_n_d &
Execute a command in the background. This operator must
follow the command, not precede it. It prints the process
identifier of the command on the standard output, so you can
use the kkiillll command to kill that process should something
go wrong. This operator lets you execute more than one
command simultaneously. For example, the command
/etc/fdformat -v /dev/fha0 &
formats a high-density, 5.25-inch floppy disk in drive 0
(that is, drive A); but while the disk is being formatted,
kksshh returns the command line prompt so you can immediately
enter another command and begin to work. If you did not use
the `&' in this command, you would have to wait until
formatting was finished before you could enter another
command.
kksshh also prints a message on your terminal when a command
that you are running in the background finishes processing.
It does not check these ``child'' processes very often,
however, so a command may have finished some time before kksshh
informs you of the fact. See the Lexicon article for the
command ppss for information on all processes; also see the
description of the built-in command jjoobbss, below.
_c_o_m_m_a_n_d && _c_o_m_m_a_n_d
Execute a command upon success. kksshh executes the command
that follows the token `&&' only if the command that
precedes it returns a zero exit status, which signifies
success. For example, the command
cd /etc
COHERENT Lexicon Page 2
ksh Command ksh
fdformat -v /dev/fha0 && badscan -o proto /dev/fha0 2400
formats a floppy disk, as described above. If the format
was successful, it then invokes the command bbaaddssccaann to scan
the disk for bad blocks; if it was not successful, however,
it does nothing.
_c_o_m_m_a_n_d || _c_o_m_m_a_n_d
Execute a command upon failure. This is identical to
operator `&&', except that the second command is executed if
the first returns a non-zero status, which signifies
failure. For example, the command
/etc/fdformat -v /dev/fha0 || echo "Format failed!"
formats a floppy disk. If formatting failed, it echoes the
message FFoorrmmaatt ffaaiilleedd! on your terminal; however, if
formatting succeeds, it does nothing.
Note that the tokens newline, `;' and `&' bind less tightly
than `&&' and `||'. kksshh parses command lines from left to
right if separators bind equally.
>_f_i_l_e
Redirect standard output. The _s_t_a_n_d_a_r_d _i_n_p_u_t, _s_t_a_n_d_a_r_d
_o_u_t_p_u_t, and _s_t_a_n_d_a_r_d _e_r_r_o_r streams are normally connected to
the terminal. A pipeline attaches the output of one command
to the input of another command. In addition, kksshh includes
a set of operators that redirect input and output into files
rather than other commands.
The operator `>' redirects output into a file. For example,
the command
sort customers >customers.sort
sorts file ccuussttoommeerrss and writes the sorted output into file
ccuussttoommeerrss.ssoorrtt. It creates ccuussttoommeerrss.ssoorrtt if it does not
exist, and destroys its previous contents if it does exist.
>>_f_i_l_e
Redirect output into a file, and append. If the file does
not exist, this operator creates it; however, if the file
already exists, this operator appends the output to that
file's contents rather than destroying those contents. For
example, the command
sort customers.now | uniq >>customers.all
sorts file ccuussttoommeerrss.nnooww, pipes its output to command uunniiqq,
which throws away duplicate lines of input, and appends the
results to file ccuussttoommeerrss.aallll.
<_f_i_l_e
Redirect input. Here, kksshh reads the contents of a file and
COHERENT Lexicon Page 3
ksh Command ksh
processes them as if you had typed them from your keyboard.
For example, the command
ed textfile <edit.script
invokes the line-editor eedd to edit tteexxttffiillee; however,
instead of reading editing commands from your keyboard, the
shell passes eedd the contents of eeddiitt.ssccrriipptt. This command
would let you prepare an editing script that you could
execute repeatedly upon files rather than having to type the
same commands over and over.
<< _t_o_k_e_n
Prepare a ``here document''. This operator tells kksshh to
accept standard input from the shell input until it reads a
line that contains only _t_o_k_e_n. For example, the command
cat >FOO <<\!
Here is some text.
!
redirects all text between `<<\!' and `!' to the ccaatt
command. The `>' in turn redirects the output of ccaatt into
file FFOOOO. kksshh performs parameter substitution on the here
document unless the leading _t_o_k_e_n is quoted; parameter
substitution and quoting are described below.
_c_o_m_m_a_n_d 22> _f_i_l_e
Redirect the standard error stream into a file. For
example, the command
nroff -ms textfile >textfile.p 2>textfile.err
invokes the command nnrrooffff to format the contents of
tteexxttffiillee. It redirects the output of nnrrooffff (i.e., the
standard output) into tteexxttffiillee.pp; it also redirects any
error messages that nnrrooffff may generate into file
tteexxttffiillee.eerrrr.
Note in passing that a command may use up to 20 streams. By
default, stream 0 is the standard input; stream 1 is the
standard output; and stream 2 is the standard error. kksshh
lets you redirect any of these streams individually into
files, or combine streams into each other.
<&_n kksshh can redirect the standard input and output to duplicate
other file descriptors. (See the Lexicon article ffiillee
ddeessccrriippttoorr for details on what these are.) This operator
duplicates the standard input from file descriptor _n.
>&_n Duplicate the standard output from file descriptor _n. For
example,
2>&1
COHERENT Lexicon Page 4
ksh Command ksh
redirects file descriptor 2 (the standard error) to file
descriptor 1 (the standard output).
Note that each command executed as a foreground process inherits
the file descriptors and signal traps (described below) of the
invoking shell, modified by any specified redirection.
Background processes take input from the null device /ddeevv/nnuullll
(unless redirected), and ignore interrupt and quit signals.
***** File-Name Patterns *****
The shell interprets an input token that contain any of the
special characters `?', `*', or `[' as a file name _p_a_t_t_e_r_n.
? Match any single character except newline. For example, the
command
ls name?
will print the name of any file that consists of the string
nnaammee plus any one character. If nnaammee is followed by no
characters, or is followed by two or more characters, it will
not be printed.
* Match a string of non-newline characters of any length
(including zero).
ls name*
will print the name of any file that begins with the string
nnaammee, regardless of whether it is followed by any other
characters. Likewise, the command
ls name?*
will print the name of any file that consists of the string
nnaammee followed by at least one character. Unlike nnaammee*, the
token nnaammee?* insists that be followed by at least one
character before it will be printed.
~_n_a_m_e
Replace the name of user _n_a_m_e with his $HHOOMMEE directory. For
example, the command
ls -l ~norm/src
lists the contents of the _s_r_c subdirectory located under the
$HHOOMMEE directory for user nnoorrmm. This spares you from having to
know where a given user's HOME directory is located.
[_C-_c]
Enclose alternatives to match a single character. A hyphen `-
' indicates a range of characters. For example, the command
ls name[ABC]
COHERENT Lexicon Page 5
ksh Command ksh
will print the names of files nnaammeeAA, nnaammeeBB, and nnaammeeCC
(assuming, of course, that those files exist in the current
directory). The command
ls name[A-K]
prints the names of files nnaammeeAA through nnaammeeKK (again, assuming
that they exist in the current directory).
When kksshh reads a token that contains one of the above characters,
it replaces the token in the command line with an alphabetized
list of file names that match the pattern. If it finds no
matches, it passes the token unchanged to the command. For
example, when you enter the command
ls name[ABC]
kksshh replaces the token nnaammee[AABBCC] with nnaammeeAA, nnaammeeBB, and nnaammeeCC
(again, if they exist in the current directory), so the command
now reads:
ls nameA nameB nameC
It then passes this second, transformed version of the command
line to the command llss.
Note that the slash `/' and leading period `.' must be matched
explicitly in a pattern. The slash, of course, separates the
elements of a path name; while a period at the begin of a file
name usually (but not always) indicates that that file has
special significance.
***** Quoting Text *****
From time to time, you will want to ``turn off'' the special
meaning of characters. For example, you may wish to pass a token
that contains a literal asterisk to a command; to do so, you need
a way to tell kksshh not to expand the token into a list of file
names. Therefore, kksshh includes the qquuoottaattiioonn ooppeerraattoorrss `\', `"',
and `''; these ``turn off'' (or _q_u_o_t_e) the special meaning of
operators.
The backslash `\' quotes the following character. For example,
the command
COHERENT Lexicon Page 6
ksh Command ksh
ls name\*
lists a file named nnaammee*, and no other.
The shell ignores a backslash immediately followed by a newline,
called a _c_o_n_c_e_a_l_e_d _n_e_w_l_i_n_e. This lets you give more arguments to
a command than will fit on one line. For example, the command
cc -o output file1.c file2.c file3.c \
file4.c file5.c file19.c
invokes the C compiler cccc to compile a set of C source files, the
names of which extend over more than one line of input. You will
find this to be extremely helpful, especially when you write
scripts and mmaakkeeffiillees, to help you write neat, easily read
commands.
A pair of apostrophes ' ' prevents interpretation of any enclosed
special characters. For example, the command
find . -name '*.c' -print
finds and prints the name of any C-source file in the current
directory and any subdirectory. The command ffiinndd interprets the
`*' internally; therefore, you want to suppress the shell's
expansion of that operator, which is accomplished by enclosing
that token between apostrophes.
A pair of quotation marks " " has the same effect. Unlike
apostrophes, however, kksshh will perform parameter substitution and
command-output substitution (described below) within quotation
marks. Note that everything between quotation marks will be a
single argument, even if there are spaces between the tokens.
For example, the command
grep "x y" *.c
calls the string-search command ggrreepp to look for the string
xx<ssppaaccee>yy.
***** Scripts *****
Shell commands can be stored in a file, or _s_c_r_i_p_t. The command
COHERENT Lexicon Page 7
ksh Command ksh
ksh _s_c_r_i_p_t [ _p_a_r_a_m_e_t_e_r ... ]
executes the commands in _s_c_r_i_p_t with a new subshell kksshh. Each
_p_a_r_a_m_e_t_e_r is a value for a positional parameter, as described
below. If you have used the command cchhmmoodd to make _s_c_r_i_p_t
executable, you may omit the kksshh command.
Parameters of the form `$_n' represent command-line arguments
within a script. _n can range from zero through nine; $00 always
gives the name of the script. These parameters are also called
_p_o_s_i_t_i_o_n_a_l _p_a_r_a_m_e_t_e_r_s.
If no corresponding parameter is given on the command line, the
shell substitutes the null string for that parameter. For
example, if the script ffoorrmmaatt contains the following line:
nroff -ms $1 >$1.out
then invoking ffoorrmmaatt with the command line:
format mytext
invokes the command nnrrooffff to format the contents of mmyytteexxtt, and
writes the output into file mmyytteexxtt.oouutt. If, however, you invoke
this command with the command line
format mytext yourtext
the script will format mmyytteexxtt but ignore yyoouurrtteexxtt altogether.
Reference $* represents all command-line arguments. If, for
example, we change the contents of script ffoorrmmaatt to read
nroff -ms $* >$1.out
then the command
format mytext yourtext
will invoke nnrrooffff to format the contents of mmyytteexxtt and yyoouurrtteexxtt,
and write the output into file mmyytteexxtt.oouutt.
Commands in a script can also be executed with the . (dot)
command. It resembles the kksshh command, but the current shell
COHERENT Lexicon Page 8
ksh Command ksh
executes the script commands without creating a new subshell or a
new environment; therefore, you cannot use command-line
arguments.
***** Variables *****
Shell variables are names that can be assigned string values on a
command line, in the form
_n_a_m_e=_v_a_l_u_e
The name must begin with a letter, and can contain letters,
digits, and underscores `_'. In shell input, `$_n_a_m_e' or
`${_n_a_m_e}' represents the value of the variable. For example:
TEXT=mytext
nroff -ms $TEXT >$TEXT.out
Here, kksshh expands $TTEEXXTT before it executes the nnrrooffff command.
This technique is very useful in large, complex scripts: by using
variables, you can change the behavior of the script by editing
one line, rather than having to edit numerous variables
throughout the script.
Note that if an assignment precedes a command on the same command
line, the effect of the assignment is local to that command;
otherwise, the effect is permanent. For example,
kp=one testproc
assigns variable kkpp the value oonnee only for the execution of the
script tteessttpprroocc.
kksshh sets the following variables by default:
# The number of actual positional parameters given to the
current command.
@ The list of positional parameters ``$1 $2 ...''.
* The list of positional parameters ``$1'' ``$2'' ... (the same
as `$@' unless some parameters are quoted).
- Options set in the invocation of the shell or by the sseett
command.
? The exit status returned by the last command.
COHERENT Lexicon Page 9
ksh Command ksh
! The process number of the last command invoked with `&'.
$ The process number of the current shell.
***** Environmental Variables *****
kksshh references the following environmental variables:
CCWWDD Current working directory: this is the name of the
directory in which you are now working.
EENNVV If this variable is set at start-up, after all pprrooffiillee
files have been executed, the expanded value is used as
the shell's start-up file. It typically defines
functions and aliases.
FFCCEEDDIITT This sets the editor used by the command ffcc.
HHOOMMEE Initial working directory; usually specified in the
password file /eettcc/ppaasssswwdd.
IIFFSS Delimiters for tokens; by default space, tab, and
newline.
KKSSHH_VVEERRSSIIOONN
The current version of the Korn shell that you are using.
MMAAIILL Checked at intervals specified by environmental variable
MMAAIILLCCHHEECCKK. If file specified by this variable is new
since last checked, the shell prints ``You have mail.''
on the user's terminal. If the file has increased in
size since the last check, the shell prints ``You have
new mail.'' on the user's terminal.
MMAAIILLCCHHEECCKK
Specifies the number of seconds between checking for new
mail. If not specified, MMAAIILLCCHHEECCKK defaults to 60
seconds.
OOLLDDPPWWDD The prior working directory, if any.
PPAATTHH Colon-separated list of directories searched for
commands.
PPSS11 First prompt string, usually `$'. Note that in this
variable and PPSS22, kksshh expands the symbol ! into the
current number of the command line. For example, the
prompt kksshh !> prints the prompt kksshh _N_N> with every
command, where _N_N is the number of the current command.
This is useful when you have enabled the history feature,
as described below.
PPSS22 Second prompt string, usually `>'. kksshh prints it when it
expects more input, such as when an open quotation-mark
has been typed but a close quotation-mark has not been
COHERENT Lexicon Page 10
ksh Command ksh
typed, or within a shell construct.
PPWWDD The present working directory, i.e., the directory within
which you are now working.
SSEECCOONNDDSS
The number of seconds since the current shell was
started.
SSHHEELLLL The full path name of the shell that you are now
executing.
TTEERRMM The name of the type of terminal you are now using, as
used by various programs for reading the file
/eettcc/tteerrmmccaapp.
TTIIMMEEZZOONNEE
The current timezone you are located in, as set in your
.pprrooffiillee. This is an interesting and powerful variable;
see its entry in the Lexicon for details.
UUSSEERR The login-identifier of the user, i.e., you.
The following special forms substitute parameters conditionally:
${_n_a_m_e-_t_o_k_e_n}
Substitite _n_a_m_e if it is set; if it is not, substitute
_t_o_k_e_n.
${_n_a_m_e=_t_o_k_e_n}
Substitute _n_a_m_e if it is set; if it is not set, substitute
_t_o_k_e_n and set _n_a_m_e to equal _t_o_k_e_n.
${_n_a_m_e+_t_o_k_e_n}
Substitute _t_o_k_e_n if _n_a_m_e is set.
${_n_a_m_e?_t_o_k_e_n}
Substitute _n_a_m_e if it is set; if it is not, print _t_o_k_e_n and
exit from the shell.
***** Command Output Substitution *****
kksshh can use the output of a command as shell input (as command
arguments, for example) by enclosing the command in grave
characters ` `. For example, to list the contents of the
directories named in file ddiirrss, use the command
ls -l `cat dirs`
***** Constructs *****
kksshh lets you control the execution of programs through the
following constructs. It recognizes a construct only if it
COHERENT Lexicon Page 11
ksh Command ksh
occurs unquoted as the first token of a command. This implies
that a separator must precede each reserved word in the following
constructs; for example, newline or `;' must precede ddoo in the
ffoorr construct.
bbrreeaakk [_n]
Exit from ffoorr, uunnttiill, or wwhhiillee. If _n is given, exit from _n
levels.
ccaassee _t_o_k_e_n iinn [ _p_a_t_t_e_r_n [ | _p_a_t_t_e_r_n ] ...) _s_e_q_u_e_n_c_e;; ] ... eessaacc
Check _t_o_k_e_n against each _p_a_t_t_e_r_n, and execute _s_e_q_u_e_n_c_e
associated with the first matching _p_a_t_t_e_r_n.
ccoonnttiinnuuee [_n]
Branch to the end of the _nth enclosing ffoorr, uunnttiill, or wwhhiillee
construct.
ffoorr _n_a_m_e [ iinn _t_o_k_e_n ... ] ddoo _s_e_q_u_e_n_c_e ddoonnee
Execute _s_e_q_u_e_n_c_e once for each _t_o_k_e_n. On each iteration,
_n_a_m_e takes the value of the next _t_o_k_e_n. If the iinn clause is
omitted, $@ is assumed. For example, to list all files
ending with .cc:
for i in *.c
do
cat $i
done
iiff _s_e_q_1 tthheenn _s_e_q_2 [ eelliiff _s_e_q_3 tthheenn _s_e_q_4 ] ... [ eellssee _s_e_q_5 ] ffii
Execute _s_e_q_1. If the exit status is zero, execute _s_e_q_2; if
not, execute the optional _s_e_q_3 if given. If the exit status
of _s_e_q_3 is zero, then execute _s_e_q_4, and so on. If the exit
status of all tested sequences is nonzero, execute _s_e_q_5.
ttiimmee _s_e_q_u_e_n_c_e
Time how long it takes _s_e_q_u_e_n_c_e to execute. When _s_e_q_u_e_n_c_e
has finished exeucting, the time is displayed on the
standard output.
wwhhiillee _s_e_q_u_e_n_c_e_1 [ ddoo _s_e_q_u_e_n_c_e_2 ] ddoonnee
Execute _s_e_q_u_e_n_c_e_2 as long as the execution of _s_e_q_u_e_n_c_e_1
results in an exit status of zero.
(_s_e_q_u_e_n_c_e)
Execute _s_e_q_u_e_n_c_e within a subshell. This allows _s_e_q_u_e_n_c_e to
change the current directory, for example, and not affect
the enclosing environment.
{_s_e_q_u_e_n_c_e}
Braces simply enclose a _s_e_q_u_e_n_c_e.
***** Built-in Commands *****
kksshh executes most commands via the ffoorrkk system call, which
COHERENT Lexicon Page 12
ksh Command ksh
creates a new process. See the Lexicon articles on ffoorrkk() and
eexxeecc for details on these calls. kksshh also has the following
commands built into itself.
. _s_c_r_i_p_t
Read and execute commands from _s_c_r_i_p_t. Positional parameters
are not allowed. kksshh searches the directories named in the
environmental variable PPAATTHH to find the given _s_c_r_i_p_t.
: [_t_o_k_e_n ...]
A colon `:' indicates a ``partial comment''. kksshh normally
ignores all commands on a line that begins with a colon,
except for redirection and such symbols as $, {, ?, etc.
# A complete comment: if # is the first character on a line,
kksshh ignores all text that follows on that line.
aalliiaass [-dd] [_n_a_m_e=_v_a_l_u_e ...]
When called without arguments, aalliiaass prints all aliases and
their values. When called with a _n_a_m_e but no associated
value, then it prints the value of _n_a_m_e. When called with a
_n_a_m_e and _v_a_l_u_e combination, it associated _v_a_l_u_e with _n_a_m_e.
For example, the command
alias logout='exit'
binds the token llooggoouutt to the command eexxiitt: hereafter,
whenever you type llooggoouutt, it will be as if you typed the
eexxiitt command.
The -dd option creates an alias for a directory.
kksshh has a number of aliases set by default. See the section
AAlliiaasseess, below, for details.
bbiinndd [-mm] [_k_e_y__s_e_q_u_e_n_c_e=_b_i_n_d_i_n_g__n_a_m_e ...]
When called without arguments, list the current set of key
bindings for MicroEMACS-style editing of command lines.
When called with arguments, bind the _k_e_y__s_e_q_u_e_n_c_e to
_b_i_n_d_i_n_g__n_a_m_e.
For example, the command
bind '^[^H'=delete-word-backward
binds the editing command ddeelleettee-wwoorrdd-bbaacckkwwaarrdd to the key
sequence <eesscc><bbaacckkssppaaccee>. Note that the carat characters
in this command are literally that, not the shell's
representation of a literal <eesscc> or <bbaacckkssppaaccee> character.
When called with the -mm option, bind more than one
_b_i_n_d_i_n_g__n_a_m_e to a given _k_e_y__s_e_q_u_e_n_c_e. This lets you build
keyboard macros, to perform complex editing tasks with one
or two keystrokes.
COHERENT Lexicon Page 13
ksh Command ksh
See the section on CCoommmmaanndd-lliinnee EEddiittiinngg, below, for details.
bbuuiillttiinn _c_o_m_m_a_n_d
Execute _c_o_m_m_a_n_d as a built-in command.
ccdd _d_i_r
Change the working directory to _d_i_r. If no argument is
given, change to the home directory as set by the
environmental variable HHOOMMEE. When invoked, it also changes
the environmental variables PPWWDD and OOLLDDPPWWDD.
Using a hyphen `-' as the argument causes kksshh to change to
the previous directory, i.e., the one indicated by shell
variable OOLLDDPPWWDD. In effect, this swaps OOLLDDPPWWDD and PPWWDD, thus
allowing you to flop back and forth easily between two
directories.
eecchhoo _t_o_k_e_n ...
Echo _t_o_k_e_n onto the standard output. kksshh replaces the
command eecchhoo with the alias eecchhoo='pprriinntt'.
eevvaall [_t_o_k_e_n ...]
Evaluate each _t_o_k_e_n and treat the result as shell input.
eexxeecc [_c_o_m_m_a_n_d]
Execute _c_o_m_m_a_n_d directly rather than as a subprocess. This
terminates the current shell.
eexxiitt [_s_t_a_t_u_s]
Set the exit status to _s_t_a_t_u_s, if given, then terminate;
otherwise, the previous status is used.
eexxppoorrtt [_n_a_m_e ...]
kksshh executes each command in an _e_n_v_i_r_o_n_m_e_n_t, which is
essentially a set of shell variable names and corresponding
string values. It inherits an environment when invoked, and
normally it passes the same environment to each command it
invokes. eexxppoorrtt specifies that the shell should pass the
modified value of each given _n_a_m_e to the environment of
subsequent commands. When no _n_a_m_e is given, kksshh prints the
name of each variable marked for export.
ffcc [-ll] [-nn] [_f_i_r_s_t [_l_a_s_t]]
Draw the previously executed commands _f_i_r_s_t through _l_a_s_t
back for manipulation and possible execution. _f_i_r_s_t and
_l_a_s_t can be referenced either by their history numbers, or
by a string with which the command in question begins.
Normally, the commands are pulled into an editor for
manipulation before they are executed; the editor is defined
by the environmental variable FFCCEEDDIITT (default, eedd). The
commands in question are executed as soon as you exit from
the editor. Option -ll lists the command(s) on ssttddoouutt, and
so suppresses the editing feature. Option -nn inhibits the
default history numbers.
COHERENT Lexicon Page 14
ksh Command ksh
ffcc -ss [_o_l_d=_n_e_w] [_c_o_m_m_a_n_d]
Re-execute _c_o_m_m_a_n_d after substituting string _n_e_w for _o_l_d.
ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g ...]
Parse the _a_r_gs to See the Lexicon entry for ggeettooppttss for
details.
hhaasshh [-rr] [_n_a_m_e ...]
When called without arguments, hhaasshh lists the path names of
all hashed commands. When called with _n_a_m_e hhaasshh check to
see if it is an executable command, and if so adds it to the
shell's hash list. The -rr option removes _n_a_m_e from the hash
list.
kkiillll [-ll] [_s_i_g_n_a_l] _p_r_o_c_e_s_s ...
Send _s_i_g_n_a_l to _p_r_o_c_e_s_s. The default signal is TTEERRMM, which
terminates the process. _s_i_g_n_a_l may either be a number or a
mnemonic as #ddeeffiinneed in header file <ssiiggnnaall.hh>. When called
with the -ll option, it lists all known types of signals.
See the Lexicon entry for kkiillll for details.
lleett [_e_x_p_r_e_s_s_i_o_n]
Evaluate each _e_x_p_r_e_s_s_i_o_n. This command returns zero if
_e_x_p_r_e_s_s_i_o_n evaluates to non-zero (i.e., fails), and returns
non-zero if it evalutes to zero (i.e., succeeds). This is
useful for evaluating expressions before actually executing
them.
pprriinntt [-nnrreeuu_n] [_a_r_g_u_m_e_n_t ...]
Print each _a_r_g_u_m_e_n_t on the standard output, separated by
spaces and terminated with a newline. Option -nn suppresses
printing of the newline. Option -uu_n redirects output from
the standard output to file descriptor _n.
Note that each _a_r_g_u_m_e_n_t can contain the following standard C
escape characters: \bb, \ff, \nn, \rr, \vv, and \###. See the
Lexicon article on CC LLaanngguuaaggee for details each character's
meaning. The option -rr inhibits this feature, and the -ee
option re-enables it.
rreeaadd _n_a_m_e ...
Read a line from the standard input and assign each token of
the input to the corresponding shell variable _n_a_m_e. If the
input contains fewer tokens than the _n_a_m_e list, assign the
null string to extra variables. If the input contains more
tokens, assign the last _n_a_m_e the remainder of the input.
rreeaaddoonnllyy [_n_a_m_e ...]
Mark each shell variable _n_a_m_e as a read-only variable.
Subsequent assignments to read-only variables will not be
permitted. With no arguments, print the name and value of
each read-only variable.
COHERENT Lexicon Page 15
ksh Command ksh
rreettuurrnn [_s_t_a_t_u_s]
Return _s_t_a_t_u_s to the parent process.
sseett [-aaeeffhhkkmmnnuuvvxx [-oo _k_e_y_w_o_r_d] [_n_a_m_e ...] ]
Set listed flag. The -oo option sets _k_e_y_w_o_r_d, where _k_e_y_w_o_r_d
is a shell option.
When used with one or more _n_a_m_e_s, this command sets shell
variables _n_a_m_e to values of positional parameters beginning
with $11.
For example, the command
set -h -o emacs ignoreeof
performs the following: turns on hashing for all commands,
turns on MicroEMACS-style command-line editing, and turns
off exiting upon EOF (that is, you must type eexxiitt to exit
from the shell). sseett commands are especially useful when
embedded in your .pprrooffiillee, where they can customize kksshh to
your preferences.
For details of this command, see its Lexicon entry.
sshhiifftt
Rename positional parameter 11 to current value of $22, and so
on.
tteesstt [_o_p_t_i_o_n] [_e_x_p_r_e_s_s_i_o_n]
Check _e_x_p_r_e_s_s_i_o_n for condition _o_p_t_i_o_n. This is a useful and
complex command, with more options than can be listed here.
See its Lexicon entry for details.
ttiimmeess
Print on the standard output a summary of processing time
used by the current shell and all of its child processes.
ttrraapp [_c_o_m_m_a_n_d] [_n ...]
Execute _c_o_m_m_a_n_d if kksshh receives signal _n. If _c_o_m_m_a_n_d is
omitted, reset traps to original values. To ignore a
signal, pass null string as _c_o_m_m_a_n_d. With _n zero, execute
_c_o_m_m_a_n_d when the shell exits. With no arguments, print the
current trap settings.
ttyyppeesseett [-ffiirrxx] [+ffiirrxx] [_n_a_m_e [=_v_a_l_u_e] ... ]
When called without an argument, this command lists all
variables and their attributes.
When called with an option but without a _n_a_m_e, it lists all
variables that have the specified attribute; - tells ttyyppeesseett
to list the value of each variable and + tells it not to.
When called with one or more _n_a_m_e_s, it gives _n_a_m_e to the
listed attribute. If _n_a_m_e is associated with a _v_a_l_u_e,
ttyyppeesseett also assigns the _v_a_l_u_e to it.
COHERENT Lexicon Page 16
ksh Command ksh
ttyyppeesseett recognizes the following attributes:
-ii Store variable's value as an integer
-ff List function instead of variable
-rr Make the variable read-only
-xx Export variable to the environment
uummaasskk [_n_n_n]
Set user file creation mask to _n_n_n. If no argument is given,
print the current file creation mask.
uunnaalliiaass [-dd] _n_a_m_e ...
Remove the alias for each _n_a_m_e. The -dd option unaliases an
alias for a directory.
wwaaiitt [_p_i_d]
Hold execution of further commands until process _p_i_d
terminates. If _p_i_d is omitted, wait for all child
processes. If no children are active, this command finishes
immediately.
wwhheennccee [-vv] _n_a_m_e ...
List the type of command for each _n_a_m_e. When called with the
-vv option, also list functions and aliases.
***** Aliases *****
kksshh implements as aliases a number of commands that sshh calls as
separate executable programs. The eecchhoo alias, for instance, does
everything that /bbiinn/eecchhoo does, but kksshh does not have to ffoorrkk()
and eexxeecc() simply to echo a token. Other aliases, like ppwwdd, work
by printing the contents of shell variables. The command
/bbiinn/ppwwdd still works should you prefer it, but you must request
it by its full path name should you not wish to use the much
faster alias version.
kksshh sets the following aliases by default. If you wish, you can
use the built-in command uunnaalliiaass to make one or all of them go
away.
eecchhoo=pprriinntt
ffaallssee=lleett
ffuunnccttiioonnss=ttyyppeesseett -ff
hhiissttoorryy=ffcc -ll
iinntteeggeerr=ttyyppeesseett -ii
llooggiinn=eexxeecc llooggiinn
nneewwggrrpp=eexxeecc nneewwggrrpp
ppwwdd=pprriinntt -rr $PPWWDD
rr=ffcc -ss
ttrruuee=:
ttyyppee=wwhheennccee -vv
COHERENT Lexicon Page 17
ksh Command ksh
***** Job Control *****
kksshh lets you manipulate and monitor background jobs via its _j_o_b
_c_o_n_t_r_o_l commands.
The following commands manipulate background jobs:
jjoobbss Display information about all controlled jobs. Information
is in the following format:
%_n_u_m [+-] _p_i_d _s_t_a_t_u_s _c_o_m_m_a_n_d
where _n_u_m indicates the job number, `+' indicates the
current job, `-' indicates the previous job, _p_i_d is the
job's process identifier, _s_t_a_t_u_s shows the status of the job
(e.g., Running, Done, Killed), and _c_o_m_m_a_n_d is the command
description. Note that kksshh only checks for changes in job
status when waiting for a command to complete.
kkiillll [-_s_i_g_n_a_l] _p_i_d ...
Described above.
wwaaiitt [_p_i_d]
Hold execution of further commands until process _p_i_d
terminates. See its Lexicon entry for details.
The following `%' syntax can be used with the above commands:
%+ Select the current job.
%- Select the previous job.
%_n_u_m Select the job with job number _n_u_m.
%_s_t_r_i_n_g
Select the most recently invoked job whose command begins
with _s_t_r_i_n_g.
%?_s_t_r_i_n_g
Select the most recently invoked job whose command contains
_s_t_r_i_n_g.
***** Command-line Editing *****
One of the most useful features of kksshh is its ability to remember
commands that you have typed previously. You can interactively
edit previously issued commands and re-issue them with just a few
keystrokes.
You can recall commands and edit them using the ffcc command,
described above. kksshh, however, also has built into it a
MicroEMACS editing feature that lets you recall and edit commands
using MicroEMACS-style editing commands. When you have finished
editing, simply typing <eenntteerr> dispatches the command for re-
execution.
COHERENT Lexicon Page 18
ksh Command ksh
To turn on MicroEMACS editing, use the command
set -o emacs
The following table gives each editing command and its default
keybinding. Note that you can replace any of the following
keybindings by using the bbiinndd command, described above. Note,
too, that not every command has a default keybinding. Those that
do not have one are marked ``None''.
aabboorrtt (<ccttrrll-GG>)
Abort the current input line or function.
aauuttoo-iinnsseerrtt
Insert text into the command line. This is the default for
almost every key.
bbaacckkwwaarrdd-cchhaarr (<ccttrrll-BB>)
Move the cursor one character to the left.
bbaacckkwwaarrdd-wwoorrdd (<eesscc>BB)
Move the cursor one word to the left. A wwoorrdd is defined as
any cluster of characters delineated by any of the
characters named in the environmental variable IIFFSS: by
default, <ssppaaccee>, <ttaabb>, and <nneewwlliinnee>.
bbeeggiinnnniinngg-ooff-lliinnee (<ccttrrll-AA>)
Move the cursor to the leftmost position (i.e., the
beginning) of the line.
ccoommpplleettee (<eesscc><eesscc>)
Complete as much as is unique of the hashed command name or
file name in which the cursor is positioned. If no unique
command or file name is found, kksshh beeps. Note that this
command does nothing unless you have used the sseett command to
turn on hashing.
ccoommpplleettee-ccoommmmaanndd (<ccttrrll-XX><eesscc>)
Automatically complete as much as is unique of the hashed
command name. Like the ccoommpplleettee command, above, except that
file names are not expanded.
ccoommpplleettee-ffiillee (<ccttrrll-XX><ccttrrll-XX>)
Automatically complete as much as is unique of the file
name. Like the ccoommpplleettee command, above, except that
commands are not expanded.
ddeelleettee-cchhaarr-bbaacckkwwaarrdd (<ccttrrll-HH>)
Delete the character to the left of the cursor. Shift text
to the left to fill the gap left by the deleted character.
COHERENT Lexicon Page 19
ksh Command ksh
ddeelleettee-cchhaarr-ffoorrwwaarrdd (<ccttrrll-DD>)
Delete the character upon which the cursor is positioned.
Shift text to the left to fill the gap left by the deleted
character.
ddeelleettee-wwoorrdd-bbaacckkwwaarrdd (<ccttrrll-WW>)
Delete the word to the left of the cursor. Shift text to
the left to fill the gap left by the deleted word.
ddeelleettee-wwoorrdd-ffoorrwwaarrdd (<eesscc>DD)
Delete the word to the right of the cursor. Shift text to
the left to fill the gap left by the deleted word.
ddoowwnn-hhiissttoorryy (<ccttrrll-NN>)
Scroll to the next command in the history buffer, if any.
eenndd-ooff-lliinnee (<ccttrrll-EE>)
Move the cursor to the rightmost position (i.e., the end) of
the line.
eeoott (<ccttrrll-_>)
Send an EOT (end of transmission) signal to the shell.
Normally, this is sent by <ccttrrll-DD>, but MicroEMACS mode
binds this keystroke to an editing command.
ffoorrwwaarrdd-cchhaarr (<ccttrrll-FF>)
Move the cursor one character to the right.
ffoorrwwaarrdd-wwoorrdd (<eesscc>FF)
Move the cursor one word to the right.
kkiillll-lliinnee (<ccttrrll-UU>)
Delete (i.e., erase) this entire input line.
kkiillll-ttoo-eeooll (<ccttrrll-KK>)
Kill the input line from where the cursor is positioned to
the end of the line.
lliisstt (<eesscc>?)
Display a sorted listed of all hashed commands and file
names that have been entered so far, and so lists the tokens
that can be expanded with the ccoommpplleettee commands, described
above.
lliisstt-ccoommmmaanndd (<ccttrrll-XX>?)
List all hashed commands.
lliisstt-ffiillee (none)
List all files used in hashed commands so far.
nneewwlliinnee (<ccttrrll-JJ> or <ccttrrll-MM>)
Dispatch the current line to the shell for execution. The
cursor need not be at the beginning or end of the line for
this command to work correctly.
COHERENT Lexicon Page 20
ksh Command ksh
pprreeffiixx-11 (<eesscc>)
Introduce a two-character command sequence.
pprreeffiixx-22 (<ccttrrll-XX>)
Introduce a two-character command sequence.
qquuoottee (<ccttrrll-^>)
Read the following character literally, rather than as an
editing command.
rreeddrraaww (<ccttrrll-LL>)
Redisplay the prompt and the current command line. This is
useful if the line is garbled due to, say, line noise when
you are using a modem.
sseeaarrcchh-cchhaarraacctteerr (<ccttrrll-]>)
Search forward in the current command line for the next
character typed.
sseeaarrcchh-hhiissttoorryy (<ccttrrll-RR>)
Enter incremental-search mode and search backwards through
the history buffer. aabboorrtt aborts search and returns you to
the line from which you began the search; <eesscc> ends
searching and leaves you in the current line.
ssttuuffff (none)
Take a character that is bound to an editing command and
``stuff'' it back into the terminal input, so it can receive
special treatment by the terminal handler.
ssttuuffff-rreesseett (none)
``Stuffs'' a character, then aborts input.
ttrraannssppoossee-cchhaarrss (<ccttrrll-TT>)
Swap the character the cursor in on, with the character to
its left.
uupp-hhiissttoorryy (<ccttrrll-PP>)
Move to the previous line in the history buffer (if any).
yyaannkk (<ccttrrll-YY>)
Insert the most recently killed text back into the command
string, at the point where the cursor is positioned.
yyaannkk-ppoopp (<eesscc>YY)
Yank a string, then replace it within the ``yank'' buffer
with the next most previously killed string.
***** Example *****
The following C code creates a program called sspplluurrtt.cc. It
demonstrates numbered redirection of kksshh, by writing to five
streams without opening them. Compile it with the command:
COHERENT Lexicon Page 21
ksh Command ksh
cc -o splurt splurt.c
To call it from the command line, you could type a command of the
form:
splurt 3> splurt3 4> splurt4 5> splurt5 6> splurt6 7> splurt7
This will redirect the sspplluurrtt's output into files sspplluurrtt33 through
sspplluurrtt77.
#include <stdio.h>
main()
{
int i;
char buf[50];
for(i = 3; i < 8; i++) {
sprintf(buf, "For fd %d\n", i);
write(i, buf, strlen(buf));
}
}
***** Files *****
/eettcc/pprrooffiillee -- System-wide initial commands
$HHOOMMEE/.pprrooffiillee -- User-specific initial commands
/ddeevv/nnuullll -- For background input
***** See Also *****
bbiinndd, ccoommmmaannddss, dduupp(), eennvviirroonn, eexxeecc, ffoorrkk(), ggeettooppttss, jjoobbss,
kkiillll, llooggiinn, nneewwggrrpp, sseett, sshh, ssiiggnnaall(), tteesstt, wwaaiitt
_I_n_t_r_o_d_u_c_t_i_o_n _t_o _s_h, _t_h_e _B_o_u_r_n_e _S_h_e_l_l, tutorial
***** Notes *****
This version of kksshh offers a subset of the features of the Korn
shell shipped with UNIX System V.2. It does _n_o_t offer the
following features:
-> vvii-style command-line editing.
-> Command ffcc -ee.
-> Variables RRAANNDDOOMM and PPPPIIDD.
COHERENT Lexicon Page 22
ksh Command ksh
-> Variable arrays.
-> Variable attributes other than integers.
The Mark Williams version of kksshh is based on the public-domain
version of the Korn shell, which in turn is based on the public-
domain version of the seventh edition Bourne shell written by
Charles Forsyth and modified by Eric Gisin, Ron Natalie, Arnold
Robbins, Doug Gwyn, and Erik Baalbergen.
COHERENT Lexicon Page 23
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