1exec(1)                          User Commands                         exec(1)
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NAME

6       exec, eval, source - shell built-in functions to execute other commands
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SYNOPSIS

9   sh
10       exec [argument]...
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12
13       eval [argument]...
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16   csh
17       exec command
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19
20       eval argument...
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23       source [-h] name
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26   ksh
27       *exec [argument]...
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29
30       *eval [argument]...
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33   ksh93
34       +exec [-c] [-a name] [command [argument ... ]]
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36
37       +eval [argument]...
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DESCRIPTION

41   sh
42       The  exec  command  specified  by the arguments is executed in place of
43       this shell without creating a new process. Input/output  arguments  and
44       appear  and,  if  no  other  arguments  are  specified, cause the shell
45       input/output to be modified.
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47
48       The arguments to the eval built-in are read as input to the  shell  and
49       the resulting command(s) executed.
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51   csh
52       exec executes command in place of the current shell, which terminates.
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54
55       eval reads its arguments as input to the shell and executes the result‐
56       ing command(s). This is usually used to execute commands  generated  as
57       the result of command or variable substitution.
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59
60       source  reads commands from name. source commands can be nested, but if
61       they are nested too deeply the shell can run out of  file  descriptors.
62       An  error  in  a sourced file at any level terminates all nested source
63       commands.
64
65       -h    Place commands from the file name on  the  history  list  without
66             executing them.
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68
69   ksh
70       With  the  exec built-in, if arg is specified, the command specified by
71       the arguments is executed in place of this shell without creating a new
72       process.  Input/output  arguments  can  appear  and  affect the current
73       process. If no arguments are specified the effect of this command is to
74       modify  file  descriptors as prescribed by the input/output redirection
75       list. In this case, any file descriptor numbers greater than 2 that are
76       opened with this mechanism are closed when invoking another program.
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78
79       The  arguments to eval are read as input to the shell and the resulting
80       command(s) executed.
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82
83       On this man page, ksh(1) commands that are preceded by  one  or  two  *
84       (asterisks) are treated specially in the following ways:
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86           1.     Variable  assignment  lists  preceding the command remain in
87                  effect when the command completes.
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89           2.     I/O redirections are processed after variable assignments.
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91           3.     Errors cause a script that contains them to abort.
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93           4.     Words, following a command preceded by ** that  are  in  the
94                  format  of a variable assignment, are expanded with the same
95                  rules as a variable assignment. This means that  tilde  sub‐
96                  stitution  is  performed after the = sign and word splitting
97                  and file name generation are not performed.
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99   ksh93
100       exec is a special built-in command that can be used to manipulate  file
101       descriptors or to replace the current shell with a new command.
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103
104       If  command is specified, then the current shell process is replaced by
105       command rather than running command and waiting  for  it  to  complete.
106       There  is  no  need  to use exec to enhance performance since the shell
107       implicitly uses the exec mechanism internally whenever possible.
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109
110       If no operands are specified, exec can be used to open or close  files,
111       or  to  manipulate  file  descriptors  from 0 to 9 in the current shell
112       environment using the standard redirection mechanism available with all
113       commands.  The  close-on-exec  flags  is set on file descriptor numbers
114       greater than 2 that are opened this way so that they  are  closed  when
115       another program is invoked.
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117
118       Because  exec  is a special command, any failure causes the script that
119       invokes it to exit. This can be prevented by  invoking  exec  from  the
120       command  utility.
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122
123       exec  cannot  be  invoked from a restricted shell to create files or to
124       open a file for writing or appending.
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126
127       eval is a shell special built-in command that constructs a  command  by
128       concatenating the arguments together, separating each with a space. The
129       resulting string is taken as input to the shell and  evaluated  in  the
130       current  environment.  command  words  are expanded twice, once to con‐
131       struct argument, and again when the shell executes the constructed com‐
132       mand. It is not an error if argument is not specified.
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134
135       On  this  manual page, ksh93 commands that are preceded by one or two +
136       symbols are special built-in commands and are treated specially in  the
137       following ways:
138
139           1.     Variable  assignment  lists  preceding the command remain in
140                  effect when the command completes.
141
142           2.     I/O redirections are processed after variable assignments.
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144           3.     Errors cause a script that contains them to abort.
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146           4.     They are not valid function names.
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148           5.     Words following a command preceded by ++  that  are  in  the
149                  format  of  a variable assignment are expanded with the same
150                  rules as a variable assignment. This means that  tilde  sub‐
151                  stitution  is performed after the = sign and field splitting
152                  and file name generation are not performed.
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OPTIONS

155   ksh93
156       The following options are supported by ksh93 exec:
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158       -a name    argv[0] is set to name for command.
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160
161       -c         Clear all environment  variables  before  executions  except
162                  variable  assignments that are part of the current exec com‐
163                  mand.
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EXIT STATUS

167   ksh
168       The following exit values are returned by exec:
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170       0        Successful completion.
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172
173       1-125    A redirection error occurred.
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176       127      command was not found.
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179       126      command was found, but it is not an executable utility.
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182   ksh93
183       The following exit values are returned by exec. If  command  is  speci‐
184       fied, exec does not return.
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186       0     Successful completion. All I/O redirections were successful.
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188
189       >0    An error occurred.
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191
192
193       The following exit values are returned by eval:
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195
196       If  argument  is  not specified, the exit status is 0. Otherwise, it is
197       the exit status of the command defined by the argument operands.
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ATTRIBUTES

200       See attributes(5) for descriptions of the following attributes:
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205       ┌─────────────────────────────┬─────────────────────────────┐
206       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
207       ├─────────────────────────────┼─────────────────────────────┤
208       │Availability                 │SUNWcsu                      │
209       └─────────────────────────────┴─────────────────────────────┘
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SEE ALSO

212       csh(1), ksh(1), ksh93(1), sh(1), attributes(5)
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216SunOS 5.11                        8 Apr 2008                           exec(1)