BSD 4_3_Tahoe development

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SH(1)               UNIX Programmer's Manual                SH(1)



N\bNA\bAM\bME\bE
    sh, for, case, if, while, :\b:, .\b., break, continue, cd, eval,
    exec, exit, export, login, read, readonly, set, shift,
    times, trap, umask, wait - command language

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
    s\bsh\bh [ -\b-c\bce\bei\bik\bkn\bnr\brs\bst\btu\buv\bvx\bx ] [ arg ] ...

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
    _\bS_\bh is a command programming language that executes commands
    read from a terminal or a file.  See i\bin\bnv\bvo\boc\bca\bat\bti\bio\bon\bn for the
    meaning of arguments to the shell.

    C\bCo\bom\bmm\bma\ban\bnd\bds\bs.\b.
    A _\bs_\bi_\bm_\bp_\bl_\be-_\bc_\bo_\bm_\bm_\ba_\bn_\bd is a sequence of non blank _\bw_\bo_\br_\bd_\bs separated
    by blanks (a blank is a t\bta\bab\bb or a s\bsp\bpa\bac\bce\be).  The first word
    specifies the name of the command to be executed.  Except as
    specified below the remaining words are passed as arguments
    to the invoked command.  The command name is passed as argu-
    ment 0 (see _\be_\bx_\be_\bc_\bv_\be(2)).  The _\bv_\ba_\bl_\bu_\be of a simple-command is
    its exit status if it terminates normally or 200+_\bs_\bt_\ba_\bt_\bu_\bs if
    it terminates abnormally (see _\bs_\bi_\bg_\bv_\be_\bc(2) for a list of status
    values).

    A _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be is a sequence of one or more _\bc_\bo_\bm_\bm_\ba_\bn_\bd_\bs separated
    by |\b|.\b. The standard output of each command but the last is
    connected by a _\bp_\bi_\bp_\be(2) to the standard input of the next
    command.  Each command is run as a separate process; the
    shell waits for the last command to terminate.

    A _\bl_\bi_\bs_\bt is a sequence of one or more _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be_\bs separated by
    ;\b;, &\b&, &\b&&\b& or |\b||\b| and optionally terminated by ;\b; or &\b&.  ;\b; and &\b&
    have equal precedence which is lower than that of &\b&&\b& and |\b||\b|,
    &\b&&\b& and |\b||\b| also have equal precedence.  A semicolon causes
    sequential execution; an ampersand causes the preceding
    _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be to be executed without waiting for it to finish.
    The symbol &\b&&\b& (|\b||\b|) causes the _\bl_\bi_\bs_\bt following to be executed
    only if the preceding _\bp_\bi_\bp_\be_\bl_\bi_\bn_\be returns a zero (non zero)
    value.  Newlines may appear in a _\bl_\bi_\bs_\bt, instead of semi-
    colons, to delimit commands.

    A _\bc_\bo_\bm_\bm_\ba_\bn_\bd is either a simple-command or one of the follow-
    ing.  The value returned by a command is that of the last
    simple-command executed in the command.

    f\bfo\bor\br _\bn_\ba_\bm_\be [i\bin\bn _\bw_\bo_\br_\bd ...] d\bdo\bo _\bl_\bi_\bs_\bt d\bdo\bon\bne\be
         Each time a f\bfo\bor\br command is executed _\bn_\ba_\bm_\be is set to the
         next word in the f\bfo\bor\br word list.  If i\bin\bn _\bw_\bo_\br_\bd ...  is
         omitted, i\bin\bn "\b"$\b$@\b@"\b" is assumed.      Execution ends when there
         are no more words in the list.

    c\bca\bas\bse\be _\bw_\bo_\br_\bd i\bin\bn [_\bp_\ba_\bt_\bt_\be_\br_\bn [ |\b| _\bp_\ba_\bt_\bt_\be_\br_\bn ] ... )\b) _\bl_\bi_\bs_\bt ;\b;;\b;] ... e\bes\bsa\bac\bc



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         A c\bca\bas\bse\be command executes the _\bl_\bi_\bs_\bt associated with the
         first pattern that matches _\bw_\bo_\br_\bd. The form of the pat-
         terns is the same as that used for file name genera-
         tion.

    i\bif\bf _\bl_\bi_\bs_\bt t\bth\bhe\ben\bn _\bl_\bi_\bs_\bt [e\bel\bli\bif\bf _\bl_\bi_\bs_\bt t\bth\bhe\ben\bn _\bl_\bi_\bs_\bt] ... [e\bel\bls\bse\be _\bl_\bi_\bs_\bt] f\bfi\bi
         The _\bl_\bi_\bs_\bt following i\bif\bf is executed and if it returns
         zero the _\bl_\bi_\bs_\bt following t\bth\bhe\ben\bn is executed.  Otherwise,
         the _\bl_\bi_\bs_\bt following e\bel\bli\bif\bf is executed and if its value is
         zero the _\bl_\bi_\bs_\bt following t\bth\bhe\ben\bn is executed.  Failing that
         the e\bel\bls\bse\be _\bl_\bi_\bs_\bt is executed.

    w\bwh\bhi\bil\ble\be _\bl_\bi_\bs_\bt [d\bdo\bo _\bl_\bi_\bs_\bt] d\bdo\bon\bne\be
         A w\bwh\bhi\bil\ble\be command repeatedly executes the w\bwh\bhi\bil\ble\be _\bl_\bi_\bs_\bt and
         if its value is zero executes the d\bdo\bo _\bl_\bi_\bs_\bt; otherwise
         the loop terminates.  The value returned by a w\bwh\bhi\bil\ble\be
         command is that of the last executed command in the d\bdo\bo
         _\bl_\bi_\bs_\bt. u\bun\bnt\bti\bil\bl may be used in place of w\bwh\bhi\bil\ble\be to negate the
         loop termination test.

    (\b( _\bl_\bi_\bs_\bt )\b)
         Execute _\bl_\bi_\bs_\bt in a subshell.

    {\b{ _\bl_\bi_\bs_\bt }\b}
         _\bl_\bi_\bs_\bt is simply executed.

    The following words are only recognized as the first word of
    a command and when not quoted.

         i\bif\bf t\bth\bhe\ben\bn e\bel\bls\bse\be e\bel\bli\bif\bf f\bfi\bi c\bca\bas\bse\be i\bin\bn e\bes\bsa\bac\bc f\bfo\bor\br w\bwh\bhi\bil\ble\be u\bun\bnt\bti\bil\bl d\bdo\bo
         d\bdo\bon\bne\be {\b{ }\b}

    C\bCo\bom\bmm\bma\ban\bnd\bd s\bsu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn.\b.
    The standard output from a command enclosed in a pair of
    back quotes (`\b``\b`) may be used as part or all of a word;
    trailing newlines are removed.

    P\bPa\bar\bra\bam\bme\bet\bte\ber\br s\bsu\bub\bbs\bst\bti\bit\btu\but\bti\bio\bon\bn.\b.
    The character $\b$ is used to introduce substitutable parame-
    ters.  Positional parameters may be assigned values by s\bse\bet\bt.
    Variables may be set by writing

         _\bn_\ba_\bm_\be=\b=_\bv_\ba_\bl_\bu_\be [ _\bn_\ba_\bm_\be=\b=_\bv_\ba_\bl_\bu_\be ] ...

    ${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br}\b}
         A _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is a sequence of letters, digits or under-
         scores (a _\bn_\ba_\bm_\be), a digit, or any of the characters *\b* @\b@
         #\b# ?\b? -\b- $\b$ !\b!.\b.  The value, if any, of the parameter is sub-
         stituted.  The braces are required only when _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br
         is followed by a letter, digit, or underscore that is
         not to be interpreted as part of its name.  If _\bp_\ba_\br_\ba_\bm_\be_\b-
         _\bt_\be_\br is a digit, it is a positional parameter.  If



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         _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is *\b* or @\b@ then all the positional parameters,
         starting with $\b$1\b1, are substituted separated by spaces.
         $\b$0\b0 is set from argument zero when the shell is invoked.

    ${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br-_\bw_\bo_\br_\bd}\b}
         If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is set, substitute its value; otherwise
         substitute _\bw_\bo_\br_\bd.

    ${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br=_\bw_\bo_\br_\bd}\b}
         If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is not set, set it to _\bw_\bo_\br_\bd; the value of
         the parameter is then substituted.  Positional parame-
         ters may not be assigned to in this way.

    ${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br?_\bw_\bo_\br_\bd}\b}
         If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is set, substitute its value; otherwise,
         print _\bw_\bo_\br_\bd and exit from the shell.  If _\bw_\bo_\br_\bd is omit-
         ted, a standard message is printed.

    ${\b{_\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br+_\bw_\bo_\br_\bd}\b}
         If _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br is set, substitute _\bw_\bo_\br_\bd; otherwise substi-
         tute nothing.

    In the above _\bw_\bo_\br_\bd is not evaluated unless it is to be used
    as the substituted string.  (So that, for example, echo
    ${d-'pwd'} will only execute _\bp_\bw_\bd if _\bd is unset.)

    The following _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs are automatically set by the shell.

         #\b#    The number of positional parameters in decimal.
         -\b-    Options supplied to the shell on invocation or by
              s\bse\bet\bt.
         ?\b?    The value returned by the last executed command in
              decimal.
         $\b$    The process number of this shell.
         !\b!    The process number of the last background command
              invoked.

    The following _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs are used but not set by the shell.

         H\bHO\bOM\bME\bE The default argument (home directory) for the c\bcd\bd
              command.
         P\bPA\bAT\bTH\bH The search path for commands (see e\bex\bxe\bec\bcu\but\bti\bio\bon\bn).
         M\bMA\bAI\bIL\bL If this variable is set to the name of a mail
              file, the shell informs the user of the arrival of
              mail in the specified file.
         P\bPS\bS1\b1  Primary prompt string, by default '$ '.
         P\bPS\bS2\b2  Secondary prompt string, by default '> '.
         I\bIF\bFS\bS  Internal field separators, normally s\bsp\bpa\bac\bce\be, t\bta\bab\bb,
              and n\bne\bew\bwl\bli\bin\bne\be.  I\bIF\bFS\bS is ignored if _\bs_\bh is running as
              root or if the effective user id differs from the
              real user id.




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    B\bBl\bla\ban\bnk\bk i\bin\bnt\bte\ber\brp\bpr\bre\bet\bta\bat\bti\bio\bon\bn.\b.
    After parameter and command substitution, any results of
    substitution are scanned for internal field separator char-
    acters (those found in $\b$I\bIF\bFS\bS) and split into distinct argu-
    ments where such characters are found.  Explicit null argu-
    ments ("" or '') are retained.  Implicit null arguments
    (those resulting from _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs that have no values) are
    removed.

    F\bFi\bil\ble\be n\bna\bam\bme\be g\bge\ben\bne\ber\bra\bat\bti\bio\bon\bn.\b.
    Following substitution, each command word is scanned for the
    characters *\b*, ?\b? and [\b[.\b. If one of these characters appears,
    the word is regarded as a pattern.  The word is replaced
    with alphabetically sorted file names that match the pat-
    tern.  If no file name is found that matches the pattern,
    the word is left unchanged.  The character .\b. at the start of
    a file name or immediately following a /\b/, and the character
    /\b/, must be matched explicitly.

    *\b*          Matches any string, including the null string.
    ?\b?          Matches any single character.
    [\b[.\b..\b..\b.]\b]
         Matches any one of the characters enclosed.  A pair of
         characters separated by -\b- matches any character lexi-
         cally between the pair.

    Q\bQu\buo\bot\bti\bin\bng\bg.\b.
    The following characters have a special meaning to the shell
    and cause termination of a word unless quoted.

         ;\b;   &\b&   (\b(   )\b)   |\b|   <\b<   >\b>   n\bne\bew\bwl\bli\bin\bne\be       s\bsp\bpa\bac\bce\be t\bta\bab\bb

    A character may be _\bq_\bu_\bo_\bt_\be_\bd by preceding it with a \\b\.\b.  \\b\n\bne\bew\bw-\b-
    l\bli\bin\bne\be is ignored.  All characters enclosed between a pair of
    quote marks ('\b''\b'), except a single quote, are quoted.  Inside
    double quotes ("\b""\b") parameter and command substitution occurs
    and \\b\ quotes the characters \\b\ '\b' "\b" and $\b$.

    "\b"$\b$*\b*"\b" is equivalent to "\b"$\b$1\b1 $\b$2\b2 .\b..\b..\b."\b" whereas
    "\b"$\b$@\b@"\b" is equivalent to "\b"$\b$1\b1"\b" "\b"$\b$2\b2"\b" .\b..\b..\b. .\b.

    P\bPr\bro\bom\bmp\bpt\bti\bin\bng\bg.\b.
    When used interactively, the shell prompts with the value of
    PS1 before reading a command.  If at any time a newline is
    typed and further input is needed to complete a command, the
    secondary prompt ($\b$P\bPS\bS2\b2) is issued.

    I\bIn\bnp\bpu\but\bt o\bou\but\btp\bpu\but\bt.\b.
    Before a command is executed its input and output may be
    redirected using a special notation interpreted by the
    shell.  The following may appear anywhere in a simple-
    command or may precede or follow a _\bc_\bo_\bm_\bm_\ba_\bn_\bd and are not



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    passed on to the invoked command.  Substitution occurs
    before _\bw_\bo_\br_\bd or _\bd_\bi_\bg_\bi_\bt is used.

    <_\bw_\bo_\br_\bd
         Use file _\bw_\bo_\br_\bd as standard input (file descriptor 0).

    >_\bw_\bo_\br_\bd
         Use file _\bw_\bo_\br_\bd as standard output (file descriptor 1).
         If the file does not exist, it is created; otherwise it
         is truncated to zero length.

    >>_\bw_\bo_\br_\bd
         Use file _\bw_\bo_\br_\bd as standard output.  If the file exists,
         output is appended (by seeking to the end); otherwise
         the file is created.

    <<_\bw_\bo_\br_\bd
         The shell input is read up to a line the same as _\bw_\bo_\br_\bd,
         or end of file.  The resulting document becomes the
         standard input.  If any character of _\bw_\bo_\br_\bd is quoted, no
         interpretation is placed upon the characters of the
         document; otherwise, parameter and command substitution
         occurs, \\b\n\bne\bew\bwl\bli\bin\bne\be is ignored, and \\b\ is used to quote the
         characters \\b\ $\b$ '\b' and the first character of _\bw_\bo_\br_\bd.

    <&_\bd_\bi_\bg_\bi_\bt
         The standard input is duplicated from file descriptor
         _\bd_\bi_\bg_\bi_\bt; see _\bd_\bu_\bp(2).  Similarly for the standard output
         using >.

    <&-  The standard input is closed.  Similarly for the stan-
         dard output using >.

    If one of the above is preceded by a digit, the file
    descriptor created is that specified by the digit (instead
    of the default 0 or 1).  For example,

         ... 2>&1

    creates file descriptor 2 to be a duplicate of file descrip-
    tor 1.

    If a command is followed by &\b& then the default standard
    input for the command is the empty file (/dev/null).  Other-
    wise, the environment for the execution of a command con-
    tains the file descriptors of the invoking shell as modified
    by input output specifications.

    E\bEn\bnv\bvi\bir\bro\bon\bnm\bme\ben\bnt\bt.\b.
    The environment is a list of name-value pairs that is passed
    to an executed program in the same way as a normal argument
    list; see _\be_\bx_\be_\bc_\bv_\be(2) and _\be_\bn_\bv_\bi_\br_\bo_\bn(7).  The shell interacts



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    with the environment in several ways.  On invocation, the
    shell scans the environment and creates a _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br for each
    name found, giving it the corresponding value.  Executed
    commands inherit the same environment.  If the user modifies
    the values of these _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs or creates new ones, none of
    these affects the environment unless the e\bex\bxp\bpo\bor\brt\bt command is
    used to bind the shell's _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br to the environment.  The
    environment seen by any executed command is thus composed of
    any unmodified name-value pairs originally inherited by the
    shell, plus any modifications or additions, all of which
    must be noted in e\bex\bxp\bpo\bor\brt\bt commands.

    The environment for any _\bs_\bi_\bm_\bp_\bl_\be-_\bc_\bo_\bm_\bm_\ba_\bn_\bd may be augmented by
    prefixing it with one or more assignments to _\bp_\ba_\br_\ba_\bm_\be_\bt_\be_\br_\bs.
    Thus these two lines are equivalent

         TERM=450 cmd args
         (export TERM; TERM=450; cmd args)

    If the -\b-k\bk flag is set, _\ba_\bl_\bl keyword arguments are placed in
    the environment, even if the occur after the command name.
    The following prints 'a=b c' and 'c':
    echo a=b c
    set -k
    echo a=b c

    S\bSi\big\bgn\bna\bal\bls\bs.\b.
    The INTERRUPT and QUIT signals for an invoked command are
    ignored if the command is followed by &\b&; otherwise signals
    have the values inherited by the shell from its parent.
    (But see also t\btr\bra\bap\bp.\b.)

    E\bEx\bxe\bec\bcu\but\bti\bio\bon\bn.\b.
    Each time a command is executed the above substitutions are
    carried out.  Except for the 'special commands' listed below
    a new process is created and an attempt is made to execute
    the command via an _\be_\bx_\be_\bc_\bv_\be(2).

    The shell parameter $\b$P\bPA\bAT\bTH\bH defines the search path for the
    directory containing the command.  Each alternative direc-
    tory name is separated by a colon (:\b:).  The default path is
    :\b:/\b/b\bbi\bin\bn:\b:/\b/u\bus\bsr\br/\b/b\bbi\bin\bn.  If the command name contains a /, the
    search path is not used.  Otherwise, each directory in the
    path is searched for an executable file.  If the file has
    execute permission but is not an _\ba._\bo_\bu_\bt file, it is assumed
    to be a file containing shell commands.  A subshell (i.e., a
    separate process) is spawned to read it.  A parenthesized
    command is also executed in a subshell.

    S\bSp\bpe\bec\bci\bia\bal\bl c\bco\bom\bmm\bma\ban\bnd\bds\bs.\b.
    The following commands are executed in the shell process and
    except where specified no input output redirection is



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    permitted for such commands.

    #\b#          For non-interactive shells, everything following the #\b#
         is treated as a comment, i.e. the rest of the line is
         ignored.  For interactive shells, the #\b# has no special
         effect.

    :\b:          No effect; the command does nothing.
    .\b. _\bf_\bi_\bl_\be
         Read and execute commands from _\bf_\bi_\bl_\be and return.  The
         search path $\b$P\bPA\bAT\bTH\bH is used to find the directory con-
         taining _\bf_\bi_\bl_\be.
    b\bbr\bre\bea\bak\bk [_\bn]
         Exit from the enclosing f\bfo\bor\br or w\bwh\bhi\bil\ble\be loop, if any.  If
         _\bn is specified, break _\bn levels.
    c\bco\bon\bnt\bti\bin\bnu\bue\be [_\bn]
         Resume the next iteration of the enclosing f\bfo\bor\br or w\bwh\bhi\bil\ble\be
         loop.  If _\bn is specified, resume at the _\bn-th enclosing
         loop.
    c\bcd\bd [_\ba_\br_\bg]
         Change the current directory to _\ba_\br_\bg. The shell parame-
         ter $\b$H\bHO\bOM\bME\bE is the default _\ba_\br_\bg.
    e\bev\bva\bal\bl [_\ba_\br_\bg ...]
         The arguments are read as input to the shell and the
         resulting command(s) executed.
    e\bex\bxe\bec\bc [_\ba_\br_\bg ...]
         The command specified by the arguments is executed in
         place of this shell without creating a new process.
         Input output arguments may appear and if no other argu-
         ments are given cause the shell input output to be
         modified.
    e\bex\bxi\bit\bt [_\bn]
         Causes a non interactive shell to exit with the exit
         status specified by _\bn. If _\bn is omitted, the exit status
         is that of the last command executed.  (An end of file
         will also exit from the shell.)
    e\bex\bxp\bpo\bor\brt\bt [_\bn_\ba_\bm_\be ...]
         The given names are marked for automatic export to the
         _\be_\bn_\bv_\bi_\br_\bo_\bn_\bm_\be_\bn_\bt of subsequently-executed commands.  If no
         arguments are given, a list of exportable names is
         printed.
    l\blo\bog\bgi\bin\bn [_\ba_\br_\bg ...]
         Equivalent to 'exec login arg ...'.
    r\bre\bea\bad\bd _\bn_\ba_\bm_\be ...
         One line is read from the standard input; successive
         words of the input are assigned to the variables _\bn_\ba_\bm_\be
         in order, with leftover words to the last variable.
         The return code is 0 unless the end-of-file is encoun-
         tered.
    r\bre\bea\bad\bdo\bon\bnl\bly\by [_\bn_\ba_\bm_\be ...]
         The given names are marked readonly and the values of
         the these names may not be changed by subsequent



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         assignment.  If no arguments are given, a list of all
         readonly names is printed.
    s\bse\bet\bt [-\b-e\bek\bkn\bnp\bpt\btu\buv\bvx\bx [_\ba_\br_\bg ...]]
         -\b-e\be If non interactive, exit immediately if a command
            fails.
         -\b-k\bk All keyword arguments are placed in the environment
            for a command, not just those that precede the com-
            mand name.
         -\b-n\bn Read commands but do not execute them.
         -\b-t\bt Exit after reading and executing one command.
         -\b-u\bu Treat unset variables as an error when substituting.
         -\b-v\bv Print shell input lines as they are read.
         -\b-x\bx Print commands and their arguments as they are exe-
            cuted.
         -\b-  Turn off the -\b-x\bx and -\b-v\bv options.

         These flags can also be used upon invocation of the
         shell.  The current set of flags may be found in $\b$-\b-.

         Remaining arguments are positional parameters and are
         assigned, in order, to $\b$1\b1, $\b$2\b2, etc.  If no arguments
         are given, the values of all names are printed.

    s\bsh\bhi\bif\bft\bt
         The positional parameters from $\b$2\b2...      are renamed $\b$1\b1...

    t\bti\bim\bme\bes\bs
         Print the accumulated user and system times for
         processes run from the shell.

    t\btr\bra\bap\bp [_\ba_\br_\bg] [_\bn] ...
         _\bA_\br_\bg is a command to be read and executed when the shell
         receives signal(s) _\bn. (Note that _\ba_\br_\bg is scanned once
         when the trap is set and once when the trap is taken.)
         Trap commands are executed in order of signal number.
         If _\ba_\br_\bg is absent, all trap(s) _\bn are reset to their ori-
         ginal values.  If _\ba_\br_\bg is the null string, this signal
         is ignored by the shell and by invoked commands.  If _\bn
         is 0, the command _\ba_\br_\bg is executed on exit from the
         shell, otherwise upon receipt of signal _\bn as numbered
         in _\bs_\bi_\bg_\bv_\be_\bc(2).  _\bT_\br_\ba_\bp with no arguments prints a list of
         commands associated with each signal number.

    u\bum\bma\bas\bsk\bk [ _\bn_\bn_\bn ]
         The user file creation mask is set to the octal value
         _\bn_\bn_\bn (see _\bu_\bm_\ba_\bs_\bk(2)).  If _\bn_\bn_\bn is omitted, the current
         value of the mask is printed.

    w\bwa\bai\bit\bt [_\bn]
         Wait for the specified process and report its termina-
         tion status.  If _\bn is not given, all currently active
         child processes are waited for.  The return code from



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SH(1)               UNIX Programmer's Manual                SH(1)



         this command is that of the process waited for.

    I\bIn\bnv\bvo\boc\bca\bat\bti\bio\bon\bn.\b.
    If the first character of argument zero is -\b-, commands are
    read from $\b$H\bHO\bOM\bME\bE/\b/.\b.p\bpr\bro\bof\bfi\bil\ble\be, if such a file exists.  Commands
    are then read as described below.  The following flags are
    interpreted by the shell when it is invoked.
    -\b-c\bc _\bs_\bt_\br_\bi_\bn_\bg  If the -\b-c\bc flag is present, commands are read from
               _\bs_\bt_\br_\bi_\bn_\bg.
    -\b-s\bs         If the -\b-s\bs flag is present or if no arguments
               remain then commands are read from the standard
               input.  Shell output is written to file descrip-
               tor 2.
    -\b-i\bi         If the -\b-i\bi flag is present or if the shell input
               and output are attached to a terminal (as told by
               _\bg_\bt_\bt_\by) then this shell is _\bi_\bn_\bt_\be_\br_\ba_\bc_\bt_\bi_\bv_\be. In this
               case the terminate signal SIGTERM (see _\bs_\bi_\bg_\bv_\be_\bc(2))
               is ignored (so that 'kill 0' does not kill an
               interactive shell) and the interrupt signal SIG-
               INT is caught and ignored (so that w\bwa\bai\bit\bt is inter-
               ruptible).  In all cases SIGQUIT is ignored by
               the shell.

    The remaining flags and arguments are described under the
    s\bse\bet\bt command.

F\bFI\bIL\bLE\bES\bS
    $HOME/.\b.profile
    /tmp/sh*
    /dev/null

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
    csh(1), test(1), execve(2), environ(7)

D\bDI\bIA\bAG\bGN\bNO\bOS\bST\bTI\bIC\bCS\bS
    Errors detected by the shell, such as syntax errors cause
    the shell to return a non zero exit status.  If the shell is
    being used non interactively then execution of the shell
    file is abandoned.  Otherwise, the shell returns the exit
    status of the last command executed (see also e\bex\bxi\bit\bt).

B\bBU\bUG\bGS\bS
    If << is used to provide standard input to an asynchronous
    process invoked by &, the shell gets mixed up about naming
    the input document.  A garbage file /tmp/sh* is created, and
    the shell complains about not being able to find the file by
    another name.








Printed 7/9/88             May 5, 1986                          9